Oil, Lubrication and Bearings

This is a topic that every one of us has probably struggled with, especially when (re)building an engine.  It’s really to your benefit to understand the issue of how engine lubrication works.  Only then can you make informed rebuild decisions, and not be at the mercy of every “expert” you happen to come across who likes to expound on the way things were done “back in the day”.  And, yes, I did once have someone extol the virtues of using a roll of toilet paper for an oil filter!  (I wonder if the brand that’s supposed to leave less fuzz on your bum would work best? Something to think about!) Engine lubrication is as much about bearings as anything else, so that’s where we’ll start.

Bearings

I’m sure that you are well aware that four-cycle gas engines typically use solid, or sliding bearings, not ball or roller bearings.  You may have wondered why.  There’s at least one good reason for this, and that is that these types of bearings concentrate force onto small areas and, while marvelous bearings for transmissions, wheels, rear ends, and other applications, they just aren’t going to stand up to the demands of an engine, especially a high-output engine.

A solid bearing might seem archaic in contrast, but a well designed solid bearing is a thing of simplistic beauty, and actually has a ton of technology involved in its design, in addition to being time tested.  The common view of a solid bearing surface is that a film of oil separates the turning journal from the stationary bearing surface.  Pretty simple, right? 

What is actually taking place is a good bit more complex than this and is rather cool, once you gain an appreciation of it.  What is happening is that we have a two- or three-layer bearing that has a soft outer surface, with a (usually) steel shell and at least one layer of a specific type of metal alloy between the shell and the bearing surface.  The relatively soft bearing surface on many bearings is referred to as “babbitt” material, named after Isaac Babbitt (patent 1252, 1839).

For the first several decades of auto production, the babbitt type bearings were poured in place, usually with the aid of a mold.  The solid babbitt material was then hand trimmed and the high spots of the bearing surface were removed.  Shims were then installed between the rod or block and cap.  As the bearing wore, shims could be removed to eliminate the excess clearance.  The separate, replaceable bearings we have today came into common usage in the 1950’s.  The application of the material may have changed, but the general nature of babbitt material remains the same.  The original babbitt material consisted of 89% tin, 9% antimony and 2% copper.  Tin-based babbitt is still popular, with a tin content of at least 80%.  Lead based babbitt will also contain some tin, but is at least 75% lead.  Generally speaking, lead babbitt is used for lesser loads and lower speeds. 

Babbitt is a relatively soft material in which is suspended crystals of a harder material.  It’s this harder material that contacts the journal at those times the journal and bearing surface are in contact.  These instances should be limited to a cold start and should not be common.  The softer material in which the crystals are suspended (tin or lead) can erode somewhat, leaving channels for oil to flow.  While this may occur, it’s not necessary for effective operation of the bearing.

In a perfect engine, this layer would never come into contact with the journal, always being separated by a film of oil.  We know that’s not the case, and that there will be contact between the journal and the bearing surface, most notably at engine start up.

With most types of bearing surfaces, it’s common practice to have the two surfaces have vastly different degrees of hardness.  This is true of ball and roller bearings, where the balls/rollers may be 1 – 2 Rockwell points harder than the races.  It’s much truer with solid or sliding bearings, where the journal is immensely harder than the bearing surface.  This allows the two surfaces to wear in such a way that they conform to one another, separated by a film of oil.  Additionally, with sliding types of bearings, you want the bearing surface to wear, not the journal.  Bearings are replaceable.

Measuring Bearing Hardness

The matter of bearing hardness was mentioned above, so it’s probably worthwhile to touch on how material hardness is measured.

The concept of measuring surface hardness by applying two different forces to a penetrator and then using the difference between the two penetration depths, termed differential depth hardness, was pioneered in the first two decades of the 20th Century. Work done by the brothers Rockwell in the U.S. followed research done by Paul Ludwik in Vienna.

The Rockwell hardness test can be performed easily, with analog or, later, digital equipment. No optical equipment is needed. There are several different scales, needed to accommodate the range of various materials and their hardness.

You will notice that the ‘N’ value is usually 100 for a diamond indenter and 130 for a ball type. The ‘h’ value is 500, with the exception of the last two entries, which are identified as ‘superficial’.

For Diamond indenter Regular Rockwell hardness: Rockwell hardness = 100 – (h / 0.002mm)

For Diamond indenter Superficial Rockwell hardness: Rockwell hardness = 100 – (h / 0.001mm)

The value ‘h’ above is in mm. Note that 1kgf = 2.204 lb. approximately.

The Rockwell hardness is calculated from the difference between the depth of the indentation after the test material has “bounced back” from the application of the total force, and its initial depth under the preliminary force. The ‘B’ and ‘C’ scales see the heaviest uses.

Engine Lubrication Regimes

Solid bearings will operate in one of three different lubrication regimes: boundary layer, mixed, or hydrodynamic.  They are designed to operate primarily in the hydrodynamic regime.  The word “hydrodynamic” has to do with the forces acting on or exerted by fluids.  This is the key to the effectiveness of this type of bearing.

Lubrication regime is far more than a journal riding on a film of oil.  The bearing is made a specific amount larger than the journal, to create a space for the oil. As the journal rotates, forces displace it from the center of the bearing.  This has the effect of creating a wedge of pressurized oil that separates the journal, in the direction of force, from the bearing surface.  It is this wedge of oil that is transferring the load of the journal to the bearing and distributing the pressure.  The key to this working effectively is the selection of the clearance value, given a knowledge of the engine speeds and loads that are expected.

This needs to be stressed: In the hydrodynamic regime the rotating part and the bearing are separated by a wedge of pressurized oil. The supply of oil and bearing clearances must be correct to allow this oil wedge to be maintained. The oil that constitutes the wedge is constantly leaking away and being replenished, removing heat as it does so. This is far more than a mere film of oil separating two parts moving relative to one another.

Depicted here is how a rotating journal interacts with the bearing and the clearance between the journal and bearing.  To simplify, we’re assuming that there is no net force displacing the journal in any particular direction.  It is precisely this action that allows the wedge of pressurized oil to form and to support the forces the journal is subject to in the hydrodynamic regime.  You can probably appreciate the fact that there must be a minimal rate of journal rotation for the hydrodynamic regime to be established and maintained.

A further method that is used to facilitate hydrodynamic lubrication is the use of bearings that have eccentricity. The journal under load being forced from center is much like the bearing being eccentric (non-circular).  If the bearing is slightly eccentric, the chosen bearing clearance can be smaller than if the bearing had been circular.  These types of bearings are thicker at the top and bottom, with the thinnest parts located at the parting lines.

Note that the horizontal dimension of the bearing is slightly larger than the vertical dimension, hence the eccentricity is oriented horizontally.  The following image should illustrate how this relates to the oil wedge with a rotating journal under load.

Boundary layer lubrication is the regime we want to avoid as much as possible.  First, realize that no surface is truly smooth, no matter how it may seem to your eye and finger. The journal may be as smooth as we can make it, but on the microscopic level, it’s truly anything but smooth.  In this regime, the oil will not be able to separate the two surfaces, and the parts of the journal and bearing surfaces that project the furthest (asperities) will interfere and collide with one another when the two surfaces are in motion relative to one another.  This will damage the surfaces, particularly the much softer bearing surface, and if the bearing were to operate continuously in this mode, it wouldn’t last long.  In addition, material from the bearing surface might transfer to the journal (galling).  In an ideal world, an engine bearing would never operate for even one second in the boundary layer regime, but that’s not practical in the real world.  Cold starts will see momentary operation in the boundary layer regime, but this is unavoidable.

The third lubrication regime is termed Mixed Lubrication.  As you might expect, it’s somewhere between the boundary and hydrodynamic regimes.  It, too, is destructive but less so than boundary lubrication.

Be sure to realize that if a bearing can’t operate hydrodynamically, it will operate on one of the two other regimes.  This could be due to any number of things, such as excessive or insufficient bearing clearances, low oil pressure, oil that is of the wrong viscosity or has too little viscosity due to excessive heat, the bearing being slightly misaligned, or a journal whose roundness or flatness is not within specification.

Although two surfaces may seem smooth, they aren’t. This image shows how asperities will collide if not separated by an oil film.

This diagram clearly shows that the lowest coefficient of friction is in the hydrodynamic lubrication regime.

Types of Solid Bearings

When rebuilding your engine, you will have the choice of either bi-metal or tri-metal bearings.  These are the number of layers on top of the steel shell.  Which type you select is related to the operating characteristics of the engine.  It’s not a matter of “If two is good, three must be better”.

Both bearing types have a steel shell.  The bi-metal have an aluminum bonding layer over the steel, with an aluminum alloy surface.  Most OEM bearings are bi-metal.

In contrast, a tri-metal bearing will have a copper alloy layer over the steel shell, followed by a copper overlay, a nickel diffusion layer and then an alloy surface of lead/tin/copper.  The top overlay is very thin, often between 0.0005” to 0.0007”.  This layer is very thin in order to remain intact under enormous pressures.  Were it thicker, it might tend to “flow” under these pressures.  Being so thin, it will eventually wear away, but the materials below this layer have sufficient qualities to perform acceptably well.

Summarizing, the tri-metal bearings are stronger, but generally will have to be replaced sooner.  For a track-only vehicle, you might choose a tri-metal and a bi-metal for an engine that will see predominantly street use.  There are no hard and fast rules.  Get good recommendations and follow them. There are some essential characteristics of modern bearings that should be considered relative to their application.

Examples of Bearing Construction and Material Configurations

• Aluminum Based Materials
  • Bi-Metal Bearings
    • Soft tin containing alloys
    • Heat treatable tin containing alloys
    • Non-heat treatable tin containing alloys
  • Tri-Metal Bearings
    • Tin-Containing Alloys
      • Soft metal overlay
    • Non-Tin-Containing Alloys
      • Soft metal overlay
      • Polymer based
      • Sputter deposited
• Copper Based Materials
  • Bi-Metal Bearings
    • Cast Copper Alloy
    • Sintered Copper Alloy
  • Tri-Metal Bearings
    • Cast Copper Alloy
    • Sintered Copper Alloy
      • Soft Metal Overlay (Lead or tin-based)
      • Sputter deposited overlays
  • Multi-Layer Bearings
    • Metallic Overlay
    • Soft Metal Overlay plus polymer-based overlay

The information above is from King Bearings (www.kingbearings.com). It’s used here to illustrate the myriad of different bearing types that might be available for a given application. Web sites like theirs are a wealth of good information.

Bearing Characteristics

• Wear Resistance Just what it says.  Oil isn’t always perfectly clean, and abrasive particles may occasionally be present.  How does a particular bearing resist damage from this?
• Fatigue Strength How much constantly repeated force can the bearing handle without the material developing cracks due to fatigue?
• Conformability How forgiving is the bearing material of slight misalignment, without impairing the oil film significantly?
• Compatibility How resistant is the bearing material to being transferred to the journal when there is direct contact between them?
• Embedability Given that there will be present small particles of dirt or debris, how well does the bearing material capture them by allowing these particles to embed themselves in it?
• Corrosion Resistance The oil will contain some amount of corrosive elements; how well does the bearing tolerate these substances?
• Cavitation Resistance How well does the bearing tolerate the forces of collapsing bubbles formed by cavitation?

Cavitation

Cavitation is the result of a liquid turning to vapor (“boiling”) when exposed to low pressure. A good example is the propeller of a submarine.  If it turns too quickly, the low-pressure areas created don’t have enough pressure for the water to remain liquid, and the water will start to convert to its gaseous state, creating bubbles.  Water needs the earth’s atmospheric pressure to remain liquid; that’s why there is no liquid water on mars, even when the temperature is above 0°C.  Subs try not to cavitate, as the sounds travel for miles and can be heard by hostile ships.  With a bearing, the collapsing of bubbles created by cavitation can be damaging to the soft load bearing surface.

This is not an engine component. It’s the propulsion unit (‘propeller’) of a nuclear submarine. There might be more than 40,000 horsepower driving this thing. All submarines are essentially stealth vehicles, their key characteristic being invisibility. Allowing its propeller to cavitate is like sending out a message to all subs and surface ships “I’m a sub and this is where I am”. Not at all good. If you’ve flown on a turboprop aircraft, you might have noticed that this bears a strong resemblance to the newer style of propeller used on some of those planes. Those are often referred to as scimitar propellers.

Solid bearings are typically bi-metal or tri-metal, with each having its own set of strengths and weaknesses. It’s not a matter of which is best as much as it is which is best for your application.

This image is of a bearing that is a thrust bearing.  In addition to functioning as one of the five crankshaft main bearings, it is the one that limits the fore/aft movement of the crank. A thrust bearing is either integrated with a specific main bearing assembly or independent of the main journal bearing. If integrated, the thrust bearing area is present in the form of flanges that extend from the front and rear of the main bearing shells. If independent, the half-moon-shaped thrust bearings are inserted separately into shallow reliefs on the front and rear of the main bearing saddle, and sometimes with the cap.

Oil grooves and holes

There has been a lot of research into the issue of the size and nature of the oil holes and grooves that are incorporated into bearing design.  Nowhere is this more true than with the main crankshaft bearings, which can be subject to extraordinary forces at times.

We’re all acquainted with the mild-performance two-bolt main caps, the high performance four-bolt mains and the (usually newer) cross-bolted mains or six-bolt mains.  These are an indication of the severity of the forces the crankshaft is expected to handle in a high performance engine.

The crank, of course, receives oil under pressure via passages in the block that provide oil to the main bearings.  The holes and groove in the main bearing allow this oil to flow into the crankshaft itself, through internal passages, and to the connecting rod journals.  That’s the only way the connecting rod journals are going to be able to receive lubrication.  The holes in the rotating crank main journals are riding over the bearing groove and are receiving a constant flow of oil from it.  Some of the oil does leak from the main bearing, like any bearing, which helps lubricate and cool the journal and bearing.

The other bearings in the engine don’t have the task of supplying oil to another location like the main does, and are therefore not in need of the bearing groove (generally).  They do, of course, have oil holes in their bearings if they receive oil under pressure from the pump (cam bearings).

Many manufacturers of high performance bearings have performed studies regarding optimal hole sizes and groove geometries.  Also, it’s not uncommon to increase the size of the openings of the oil passages in a crankshaft when it’s being prepared for high performance.

Bearing Clearances

It’s obvious that we want our bearings to be operating in the hydrodynamic regime the vast majority of the time, whether the engine is from a daily commuter or a track day car.  Bearing clearances have to be chosen by taking into account the type of operation the engine is going to see. 

With a general passenger car engine, we still desire the bearings to operate hydrodynamically.  Even though the engine speeds and loads might be unremarkable with a passenger car engine, the bearing types and clearances still need to be chosen for the application.  Given this, a typical passenger car engine is going to have somewhat larger bearing clearances than you might select for your performance engine.

The passenger car, with its lower engine speeds, should have bearing clearances chosen so that it is operating hydrodynamically at these lower engine speeds.  The slightly larger bearing clearances will help assure that this is the case.

So, it makes sense that you would just choose the smallest clearance that would work, right?  Well, maybe not.  First we should look at the ramifications of having a clearance toward the smaller side of the range and then a clearance toward the larger side of the range.

A smaller clearance results in less leakage from the bearing, and thus higher temperatures of the oil that is carrying the journal load at any particular instant in time.  With a pressurized lubrication system, the bearings will constantly lose oil, which is highly desirable.  The hotter oil that’s carrying the loads is constantly replaced with cooler oil.  If clearances are too large, the volume of leaking oil might be excessive, leading to lower than optimal oil pressure or knocking of the journal at some speeds/loads.  Yes, it will lead to lower oil temperatures at the journal-bearing interface, but the net result will be undesirable.

As you probably guessed, your performance engine is going to have bearing clearances that are somewhat smaller, given its high rpm operation.  The smaller clearance will contribute to hydrodynamic operation at the higher engine speeds.  Some expert sources specify clearances of 0.00075” to 0.0010” per 1 in. of journal diameter, plus an additional 0.0005”.  Remember that eccentric bearings will allow smaller clearances.  Always follow the manufacturer’s recommendations.

Journals can wear in different ways. Three of the most common are shown here. If rebuilding an engine, extensive inspecting and measuring of all journals should be done, with any out-of-spec condition addressed by precision grinding. This will require oversize bearings to compensate. We won’t cover this topic here.

Crush Height

This is the measurement of how high the bearing extends from its housing when it is tightly inserted (per specification), with one side of the bearing flush with the housing.  When the bearing is installed, this value will be split with one-half of it on each side.  The crush will ensure that the bearing is held in place with the designed-for amount of force.  This will not only help keep the bearing from moving, it will also ensure that the bearing is in contact with the supporting metal well enough to allow good heat transfer.  Naturally, excessive crush will distort the bearing and likely lead to bearing failure.  Crush height might be 0.001 to 0.002 for a passenger car engine and twice that for a high-performance engine.

As you might expect, I’m going to recommend that you seek expert advice, understand it, and follow it.  Feel free to communicate directly with a bearing manufacturer if you have any questions about the quality of advice you receive from your engine part supplier.

Camshaft Bearings

Camshaft bearings don’t have to handle the forces of crankshaft and connecting rod bearings, but they are still hydrodynamic bearings and the same conditions apply to them. Cam bearings are available as babbitt, bi-layer or tri-layer.  Their physical construction may be of the bushing type (cylinder) or of the split shell type.  The babbitt type has low load carrying capacity.  The bi-layer, with it aluminum alloy lining, is substantially stronger and is the go-to for most applications. 

The tri-layer is relegated to serious performance applications where cam loads are huge and the strength of a tri-layer bearing is needed, and where longevity is only a secondary consideration.

Piston Pin Bearings

Piston pin bearings (bushings) are a bit different, but have some similarities to solid bearings.  The motion of the pin relative to the bushing isn’t the same as with a crankshaft journal or a camshaft, and a hydrodynamic regime cannot be established.  The reason for this is that the piston/connecting rod/pin don’t turn continuously in the same direction relative to one another, thus the high-pressure wedge of oil doesn’t come into play.

As you may know, piston pins are generally either press fit into the small end of the connecting rod or fully floating.  In the former, the press fitting holds the pin in place and the bearing surfaces are between the pin and the pin bore in the piston.  With a fully floating pin, there are three bearing surfaces per piston.  With this arrangement, clips hold the pin in place in the piston.

With either pin method, proper lubrication must be maintained.  Pressurized lubrication can’t be used here.  Sometimes oil passages are provided within the piston, channeling oil from the oil ring groove to the bushing areas of the pistons, through holes in the bushing area.  Even if these aren’t provided, the slight movement between the piston and the pin will pull in oil as the gap between the pin and the bushing alternates between the bottom and top of the pin bore.

There are high-performance aftermarket connecting rods that have oil passages machined into the rods so that oil can be supplied to the piston pin by the connecting rod journal. Some non-automotive engines use this method as well.

Modern pistons are so cool. Compare this with a ’50’s piston, which looks pretty much like a cylinder.

Three types of clips for piston pin retention.

Get the Lead Out!

Lead has been in the process of being phased out of automotive bearings and other components for several years.  Actually, the elimination of lead is a world-wide effort, led by the European Union.  It has been particularly burdensome to the electronics industry.  Lead has always been a major component of solder, and lead-free solder is less effective in some ways.  I believe this to be utter and complete lunacy!

Lead has been used in some ways that are questionable at best.  The use of tetraethyl lead in leaded gasoline started in the 1920’s when the industry was seeking cheap ways to boost gas octane.  It is alleged, and I believe, that it was known at that time that this presented a serious health risk.  The initial alarm was raised when refinery workers were dropping dead!  The fact that this stuff was allowed to be used at all was criminal.

The water from your home faucet very well might come to you through pipes that contain lead.  I’m sure you remember the still-ongoing saga in Flint, Michigan.  The city water pipes were “cleaned”, which exposed the lead that was used for joints and such.  Levels of lead in their water vastly exceeded the recommended limit.  That’s a legitimate problem.  Lead in electronic solder and automotive bearings is not!

Consider that we are manufacturing lead-free electronics for everything, including aircraft.  Lead free solder is much more prone to the formation of dendrites, which are fine crystalline metal growths that are often invisible to the naked eye. These can form short circuits and cause the board to fail.  That’s an inconvenience if it’s with your cell phone, but if it’s a Boeing787 or a Seawolf class submarine, that’s a whole different level of pain. 

Lest you think I jest, here’s a photo of a dendrite taken under a microscope.  The dendrite is tiny and might even be invisible to the naked eye, but it can cause catastrophic failure nonetheless.

It would make sense to retain lead solder for high importance electronics, such as military, aviation, medical, etc.  But, nooooo… we have to eliminate it all and hope for the best.

The site Whisker Failures (nasa.gov) has information about tin whisker related failures in satellites and military hardware. One of the weapons systems was the AIM-54 Phoenix air-to-air missile. This 13-foot long, 1,000 pound, Mach 5 missile was carried by naval F-14 Tomcats and had a 100-mile range. The aircraft/missile system was the primary fleet defense weapons system for the US carrier fleets. If incoming threats were detected on long-range radar, F-14’s armed with up to six AIM-54s would speed at Mach 2+ to their launch points before releasing their missiles. This fleet defense function has largely been taken over by advanced surface to air missiles carried by AEGIS guided missile cruisers.

I didn’t want to overlook this opportunity to include a cool picture. This is an AEGIS ship launching a surface-to-air missile. Having built and launched model rockets with my son, I’d give my left nut to see something like this in person.

Engine Oiling Systems

Sometimes things seem so obvious that we assume, if we even think about it, that they must have always been this way.  An engine oiling system might be an example of this.

The Ford Model T didn’t have an oil pump.  There was an oil pan, and lubrication of the various engine parts was accomplished by splashing, dripping and by throwing oil due to centrifugal forces.  This was a respectable piece of engineering for 100+ years ago. What do you own that might have an engine that’s lubricated in this manner? How about the old Briggs & Stratton in your mower?

There are variations in engine oiling systems between manufacturers and between different eras. Hollow pushrods have become a standard way to oil the valvetrain for non-OHC engines. Before stamped steel, stud mounted rockers, shafts were used to mount the rocker arms and oil was supplied to them via the rocker shaft, which received oil from a passage in the head. A few of the first V8s in the 1950’s are known for having oiling systems that were problematic. In some cases, this has been addressed after the fact with oil tubes that can be installed to supplement the weak feature of the oiling system and thus overcome this issue.

Oil Pumps

Oil pumps are not things that get a lot of attention, unless you’re building a custom engine or rebuilding your classic engine for a higher performance level.

We all know the function of an oil pump, and it’s often taken for granted, unless there’s a problem.  All we need is about 10psi per 1,000 rpm, right?  That’s not wrong, but read on.

There are two general types of engine driven oil pumps.  The first is the twin gear type, which is driven most commonly by the camshaft or distributor.  One gear is driven, which in turn drives the second gear.  They typically turn at one-half the engine speed, unless driven by the crank itself.

The other type of oil pump is the type known as rotor pumps, or gerotors.  With this type of pump, the driven inner gear turns against an outside rotor.  The rotor spins at about 80% of the rate of the inner gear.  The gear and rotor together create kind of a bellows action.  The pump is either mounted in the crankcase or it’s mounted externally.  With this type of pump the mounting accuracy is critical.

Some newer performance engines have crank driven gerotor oil pumps as standard equipment.

All oil pumps have a spring and ball valve assembly to regulate the oil pressure.  With some designs the spring pressure is adjustable or the spring can be replaced with a stiffer one for a higher pressure value. Be aware that you will not need more than 60 or 70 psi, even with a 700+Hp monster engine.

Oil Pressure Problems

If your oil pressure is too high, it means that there is a problem that is probably restricting oil flow.  So, it’s not the high pressure itself that’s a danger, it’s the cause of the high oil pressure that might damage your engine.  If you are experiencing such an issue, there are a few things to check.

• Are you using oil with the recommended viscosity?  If your oil was recently changed, it’s possible that the oil change place put in a higher viscosity of oil.
• Is the bypass valve in your oil filter defective?  The only way to know is to replace the filter.
• A blocked oil passage can cause high oil pressure.  You do not want your engine to operate for long with this issue.
• Your oil pressure may seem high when it’s not if you have a faulty oil sending unit.  These fail far more often than the gauge itself.  If the meter needle is bouncing around or if it’s reading really low at times and really high at other times, it’s not really an oil pressure issue.

If your oil pressure is too low, the one of the following things might be the cause.

• Oil with too low a viscosity (If recently changed).
• Excessive bearing wear. (Obviously, this will occur gradually)
• Plugged oil filter.  Shame on you if you have allowed this to happen.  Easy fix, though.
• Severely worn or defective oil pump.
• Oil bypass in filter stuck open.
• Same comments about oil sending unit apply.

Oil Filters

It’s interesting to note that, into the 1950’s, many American cars either did not have oil filters, or offered them as optional equipment.  

The best recommendation that can be made about oil filters is to choose one that has the following qualities:

• Sufficiently large filter element (square inches when flattened out)
• Filter element is not plain paper type
• Central tube is metal, not plastic
• Bypass valve spring is actually a coil spring
• End pieces to filter element are not cardboard
• Filter element has metal support*
• Anti-drain-back valve is silicone, not rubber*

* Some would consider to be of lesser importance

Most oil filters are constructed like this image shows.  Note the flow of the oil, with dirty oil entering the holes in the periphery, going through the media, and returning through the central hole. 

Please keep in mind that we’re focusing on high quality, high performance oil filters.  Yes, they are going to be higher quality and higher price than most filters, even those that come as standard equipment on some late model performance cars.  That 2019 392 Hemi is covered by a warranty; your ‘69 426 Hemi isn’t!  It’s rare, but oil filters have been known to fail, spreading pieces of filter element throughout the engine.  I’d rather have the piece of mind knowing that’s not ever going to happen to my performance engine, whether it’s new or classic.  In all, pretty much the same philosophy as choosing an oil.

The filter element should be something more effective than plain cellulose paper, although many low- and mid-tier filter elements are just that.  The better filters have elements that are more substantial and more effective, often having sections designed to filter larger and smaller particles.  Better filters usually have a wire mesh inside the pleated element to provide added support if needed.

The more effective filters tend to have a greater amount of element area, as expressed in square inches.  Of course, every element is pleated to make the best use of available space.  However, I do believe that it’s possible to have too much element for a given enclosure size, resulting in pleats that are too tightly packed for the extra element area to be effective.  I wouldn’t worry about this as much as being aware of it in case you come across some new filter advertising an unusually large amount of filter element area.

The pleated element needs something to keep it in place, and that’s what the end pieces do.  I would not accept a filter that has these pieces made from any type of fiber type product.

The much maligned bypass valve has the purpose of allowing oil to bypass the filter media if the media is clogged or if the oil is exceptionally thick due to low temperatures.  Without it, the engine would be oil starved during these times.  I’d much, much rather feed my engine unfiltered oil than no oil at all!  Some of the uninformed seem to think the presence of such a valve is somehow indicative of a poor design, but it’s very much the contrary.

What do you mean “They Didn’t Make It”?

It’s a sad fact of life that there are fewer and fewer companies who make their own products, and nowhere is this more evident than in the automotive filter market. There are two companies who actually manufacture engine oil filters, Mann + Hummel and Champion Laboratories. Fortunately, it seems that the vast majority of oil filters are still manufactured in the USA.

There are several videos on the web that feature someone cutting open various oil filters and making something of an evaluation of the components. I suggest you check some of them out, as I found many of them enlightening. There can be huge differences between the quality of materials. This will generally be reflected by the price of the filter, but don’t blindly assume that an expensive filter is better than one of lesser cost. Also, don’t fall for the marketing techniques of many of these companies. Just because Dale Earnhardt used a particular product doesn’t mean much regarding its ultimate quality and value. If advertising were true, I should be irresistible to the ladies, because I drink the right beer!

Finally, I’ll mention that I don’t buy auto components made in communist China, if I have a choice, which I usually do. Call me weird, but I don’t believe in supporting the economy of a country that has values that are so opposite those of most civilized countries.

Windage Trays

Windage (“win-dij”) is the effect of the rotating crankshaft assembly and the reciprocating pistons experiencing air resistance.  This is further complicated by the storm of oil droplets that are, at any instant, moving through the crankcase.  The power losses can be substantial, especially at high engine speeds.  Additional losses can come from oil on the crankshaft adding mass to the rotating assembly.

The windage tray is a baffled sheet or a screen that exists to shield the rotating crank assembly from the oil in the bottom of the oil pan.  It prevents the crank from contacting the oil in the sump, which otherwise would cause drag on the crank as well as aerate the oil.

Oil Scrapers

This is a shaped piece of sheet metal that often mounts to the pan rail.  Its function in life is different from the windage tray, but complementary to it.  The oil scraper sits close to the rotating crank and thick films of oil that may be on the crank are scraped off and allowed to return to the sump.  The benefits of an oil scraper are primarily seen at high engine speeds.

Oversize Oil Pans

One way to ensure your oil pump will never be starved for oil (especially if you’re running a high-volume type) is to use a larger pan.  There are numerous makers of aftermarket oil pans that have a higher capacity than the stock pans.  I counted over ten manufacturers and 2,000+ products on the http://www.summitracing.com web page for “oil pans”.  You can go to a pan that allows an extra two or more quarts and not even have to sacrifice ground clearance, with some of the models that are available.

You absolutely, positively do not want to “simulate” a larger pan by overfilling your stock oil pan.  This will introduce windage problems and will accomplish nothing positive.  If anyone suggests this, they might be an imbecile.

There are oil pans available for track activities that involve frequent high-g cornering.  These not only have a higher capacity, but they also have provisions for keeping the oil near the pickup during hard cornering.

Be aware that an aftermarket oil pan may require you to relocate your oil filter.  The manufacturers literature should provide all of the details, and some of them offer the kit/parts needed.

Oil Coolers

An oil cooler Is a darn good thing to have.  The only downside is that it is another thing to fail, but I still recommend them wholeheartedly.  These fall into two different types: oil-to-air and oil-to-water.  The former is a small radiator, some of which come with their own fan.  Sometimes mounting one can be a bit of a challenge, but there’s plenty of information available from the manufacturer or online.

Oil Accumulators

This is a cylindrical device that holds oil.  The oil pump fills it when the engine is in normal operation, and this oil remains there, under pressure from a device located in the back end of the cylinder.  When you start your engine, the accumulator will supply oil and thus help prevent the wear that your bearings would otherwise incur (until the pump pressure came up).

It will do so more than that, though.  If and when your engine experiences a momentary drop in oil pressure, say due to a sustained high-G curve, the oil in the accumulator will be forced out by the difference in pressure between it and the pressure of the oil system.  That mode of operation might not be something that many of us experience, but if this is you with your car, this is something to think about.  Some people view the engine startup benefits of an oil accumulator enough to merit installing one.

Dry Sump Systems

If you have a vehicle that sees regular track time, then you ought to consider this modification to your engine.  This mod isn’t something that you take on lightly.  It’s expensive.

What a dry sump does, though, is just about guarantee you that your engine will never have oil supply or pressure issues related to any forces the vehicle experiences.  You could high-G corner till you puked and your oil system will be perfectly happy.

With a dry sump, the oil pan isn’t the reservoir of oil that it is with a wet sump setup.  The pan itself is much more shallow and lacks the deep sump part of an ordinary pan.  An external, crank driven oil pump pulls the oil from the pan and supplies it to a five- to six-quart external tank.  The pump turns at a lower speed than the crank.  From here, the oil is supplied to the oiling system.  There is no conventional oil pickup in the pan that can become uncovered under some hard maneuvering conditions.  Also, the greater total oil capacity this system provides can benefit you with cooler oil, as well as cleaner oil.

You might question the last statement.  If you’re dry-sumping it and are using, say, seven quarts of oil as opposed to five quarts in the wet-sump equivalent engine, these seven quarts are going to be subject to the same amount of contamination as the five quarts in the other engine.  However, each of the seven quarts will be ‘cleaner’ than any of the five quarts from the other engine, right?  In fact, I’d say that if we had a ten quart setup, each quart of oil would have half of the contaminants compared to a quart from the wet sump engine.

 Dry-Sump Advantages over a Wet-Sump

The primary advantages include:

• Prevention of the engine experiencing oil starvation during high g-loads when oil sloshes, which improves engine reliability. Most engines can be damaged by even brief periods of oil starvation. This is the reason why dry sumps were invented, and is particularly valuable in racing cars, high performance sports cars, and aerobatic aircraft that regularly experience high accelerations. Oil slosh occurs in dry-sump systems too, but it is much easier to design a remote reservoir to tolerate high amounts of slosh, by being tall and narrow, and having large baffles.
• Increased oil capacity by using a large external reservoir, beyond the limits of a wet-sump system.
• Improvements to vehicle handling and stability. The vehicle’s center of gravity can be lowered by mounting the (typically very heavy) engine lower in the chassis due to a shallow sump profile. A vehicle’s overall weight distribution can be modified by locating the external oil reservoir away from the engine.
• Improved oil temperature control. This is due to increased oil volume providing resistance to heat saturation, the positioning of the oil reservoir away from the hot engine, and the ability to include cooling capabilities between the scavenger pumps and oil reservoir and also within the reservoir itself.
• Improved oil quality. When oil sloshes against the crankshaft and other high-speed spinning parts, it causes aeration of the oil.  Aerated oil protects engine components far less effectively. A dry-sump system minimizes oil aeration, and also de-aerates oil far more effectively by pumping it first into a remote reservoir.
• Increased engine power. In a wet-sump engine, oil slosh against spinning parts causes substantial viscous drag which creates parasitic power loss. A dry-sump system removes oil from the crankcase, along with the possibility of such viscous drag. More complex dry-sump systems may scavenge oil from other areas where oil may pool, such as in the valvetrain. Power can be further increased if the dry-sump system is designed to create a vacuum inside the crankcase, which reduces air drag (or windage) on moving parts as well.
• Improved pump efficiency to maintain oil supply to the engine. Since scavenge pumps are typically mounted at the lowest point on the engine, the oil flows into the pump intake by gravity rather than having to be lifted up into the intake of the pump as in a wet-sump. Furthermore, scavenge pumps can be of a design that is more tolerant of entrapped gasses than the typical pressure pump, which can lose suction if too much air mixes into the oil. Since the pressure pump is typically lower than the external oil tank, it always has a positive pressure on its suction regardless of cornering forces.
• Having the pumps external to the engine makes them easier to maintain or replace.

Source: https://en.wikipedia.org/wiki/Dry_sump

There are disadvantages to dry sump systems, of course. I mean, there had to be, right?

• Most significantly, these systems are expensive. You should plan on spending well north of $3,000 for a dry sump system.
• The additional hardware (and oil) adds weight, complexity, and maintenance. The oil canister can be challenging to locate.
• Some engine components are designed to be splash lubricated. Without the splash lubrication, other provisions have to be made to lubricate these engine parts.

Here’s a representation of a dry sump system.

Motor Oil

What is the purpose of oil in your engine?  If you said “lubrication”, you are 90% correct as that’s the primary purpose.  But what about cooling?  There are areas within the engine, such as the oil between a journal and bearing, that reach temperatures much higher than the average temperature of the oil.  The leaking of oil from this area, with the replenishment of fresh oil, carries this heat away to the oil in the pan, then from the pan itself to the ambient air.  Without this cooling effect, the engine would not last long.

Finally, the engine oil serves a third purpose.  This is to help seal the piston ring to cylinder wall gap.  Yes, it’s pretty minimal to begin with, but the oil does enhance the sealing ability of the rings. Certainly, this third purpose is of far less importance than lubrication and cooling.

As you may already know, motor oil has changed substantially over the years and the options today are more numerous than ever.  Like most things automotive, the present offerings are a reflection of what occurred prior.  Knowing the story helps you appreciate today’s products and to make informed decisions regarding the products you choose.

The Continuous Oil Refining Company was formed in 1866, and their initial petroleum offerings were aimed at “improving health”.  While bizarre, this was rather common for the day.  Coca-Cola was created for the same purpose, as a health elixir.  There were literally hundreds of different products being offered for specific ailments or for “anything that ails you”.  Maybe half were just outright scams, with the other half being naive.

This product didn’t last long, with the company having come to the realization that they had the basis for a lubricant that was superior to what was presently being used for steam locomotives.  As a pure petroleum-based lubricant, it would outperform other contemporary lubricants, especially at high temperatures.  Of course, when automobiles came along a couple of decades later, it was only natural that this pure petroleum-based oil would be used for its lubrication needs.

What Exactly is Oil?

Crude oil from the ground is a compound of carbon and hydrogen, formed several tens of millions of years ago or longer.  The majority of known oil deposits date from the Mesozoic era, which spanned from 150mya to 65mya.

Ancient sea bottoms were covered with plankton, algae and plants, then buried by sediments.  Over time, the enormous pressures and temperatures formed deposits of oil, tar, coal and natural gas.  While oil deposits do exist under the floors of areas like the North Sea, this isn’t the body of water present when the initial plant and animal deposits were made.  Of course, there are many deposits under what is now land.

Oil and coal reflect the nature of the materials that they were created from, as well as the specific conditions.  Two different deposits of oil or coal can vary significantly in a number of characteristics, making some sources better than others for a given purpose.  For instance, some sources of crude oil have characteristics that make it easier to create from them a quality motor oil.

Oil has to be refined into a product suitable for our uses today.  The base crude oil contains the following elements, and their approximate percentages.

• Carbon                          84%
• Hydrogen                     14% (lightest element in the universe)
• Sulfur                            1-3% (in compounds)
• Nitrogen                       <1% (our atmosphere is 78% nitrogen)
• Oxygen                         <1%
• Metals                           <1%
• Salts                              <1% What is a salt?

Salts?

The presence of salts in oil seemed a bit strange. But salt is mined in the ground, right, so maybe it’s not so weird. It got me thinking, though (I know!). I knew that underground salt deposits were left by ancient seas, but I wasn’t sure where salt itself came from. The oceans are salty, sure, but where does the salt come from in the first place?

The sea takes in dissolved matter from rivers that enter it and volcanic activity on the seafloor. The rivers mainly provide ions from the weathering of rocks – unpaired atoms with a lack or excess of electrons. The major ions are various silicates, carbonates, and the alkali metals sodium, calcium and potassium. Seafloor volcanoes are sources of mainly hydrogen and chloride ions.

Sodium ions from rivers and chloride ions from volcanoes combine in sea water and drop out when they become concentrated enough. They precipitate as solid salt, sodium chloride, the mineral halite. Of course, when sea water evaporates the minerals remain.

As oil was originally used for engines, it consisted of straight refined oil.  Additives had yet to be developed.  The Society of Automotive Engineers, in the US, defined a standard measure of viscosity.  Specifically, the viscosity of an oil was measured at 100°C.  It’s said that this is the temperature reached by oil in the connecting rod/crank throw bearings (and it may be), but it seems a little conveniently round to me.  Regardless, that’s the temperature of interest when measuring viscosity.

Oil Additives

Beside the natural oil base, there are a number of additives to oil.  These fall into the following categories:

• Anti-wear additives
• Dispersants
• Viscosity Index Improvers
• Detergents
• Corrosion and oxidation inhibiters

Detergent has been added to oil going back to the 1930’s.  These are intended to neutralize oil impurities so that sludge doesn’t form.

Corrosion and Rust Inhibitors are added just for that purpose–to prevent these two things that are both types of oxidation and affect the internal metal of the engine.

Antioxidants are used to prevent the oil from oxidizing.  This is different from the above in that it concerns the oil itself, not engine metal.

There are substances known as metal deactivators, whose function is to coat metal surfaces to prevent the metal and oil contacting and the oxidation that results.

Bases are added to oil to counterbalance the acids that tend to form in engine oil.  Exposure to air and to combustion gasses that bypass the rings can cause the oil to become acidic.  Alkaline additives are used for this purpose.

Antiwear Additives are added to coat metal parts and inhibit metal-to-metal contact.  Zinc based compounds are used here almost exclusively.

Dispersants are additives that keep substances such as soot suspended in the oil, where they will have less chance to be harmful.

Anti-Foam Additives inhibit the ability of the oil to form air bubbles.

There are aftermarket or over the counter oil additives that are sold in every auto parts store.  The most famous of these is STP Oil Treatment, which has been around seemingly forever.  Slick50 made its appearance in the ‘80’s, if I recall correctly.  I’ve used oil additives on occasion, but like most people, I am incapable of objectively evaluating any such additive.

Oil Additive Products – Useful?

Oil additives belong in a group of seemingly unrelated products in that their value to any given consumer is strongly based on that person’s predisposition, experience, and personality. It’s easy to tell whether Hunts or Heinz has the ‘best’ ketchup, but what about things like high-end audio cables, really expensive guns, mileage improvement devices and oil additives? Opinion is as strong as objective information is absent. Try as you might to be an objective judge, your satisfaction with products like these will be hugely influenced by your predisposition toward being believing or skeptical.

At the risk of stepping on toes, I’m going to express some thoughts about oil additives. STP has been bought and sold several times over the years. Both STP’s parent company and Slick 50’s have been sued successfully by the Federal Trade Commission (STP more than once) for false advertising. In addition, many oil additives contain compounds already found in oil. Finally, many additives seem to have a primary purpose of increasing the oil viscosity. Why would you do that rather than simply use an oil of the proper viscosity in the first place?

There are aftermarket or over the counter oil additives that are sold in every auto parts store.  The most famous of these is STP Oil Treatment, which has been around seemingly forever.  Slick50 made its appearance in the ‘80’s, if I recall correctly.  I’ve used oil additives on occasion, but like most people, I am incapable of objectively evaluating any such additive.

Society of Automotive Engineers

Anyone who has looked at a jug of oil has noticed the “SAE” designations on the label.  But what exactly is the SAE?

Most of us know SAE from engine oil and from tool standards.  If a socket set isn’t metric, it’s “SAE”.  The SAE is involved in all things automotive, and was founded in New York City in 1905.  Henry Ford was their first vice president.  SAE 30 weight was the first standardized oil viscosity, and it was acceptable to temperatures as low as -10°C (14°F).  Given that there are huge areas of the U.S. that can experience daily temperatures this low and lower during several months of the year, people were required to change to a heavier weight prior to winter and then to change back to 30 weight before the summer heat.  Not too convenient.

Leveraging on the strides made during the war, oil producers discovered that they could add to their oil substances that were derived from oil that had a structure of long chains of carbon and hydrogen molecules.  These so-called polymers could do almost miraculous things for engine oil, like making the oil act like a thinner, lower viscosity oil when cold, but reverting back to its base viscosity when hot.  No more having to change oil twice a year simply because of ambient temperature changes.  In addition, these polymers could vastly increase the shear strength of oil, which is a quality that relates to how oil under pressure (between a journal and a bearing) stands up.  Of course, this is of particular interest in race engines.

Viscosity Modifiers (also known as Viscosity Index Improvers) were described above.  They improve the Viscosity Index, which allows a thinner oil to behave like a thicker oil at high temperatures.  These substances have a shear stability index (SSI), where lower is better.  VMs will “wear out” as oil is used.

Synthetic Oils

Engine oil doesn’t have to be made from crude oil anymore.  There is a family of chemicals known as poly alpha olefins that can be used as an oil base.  PAO’s, as they came to be known, were a byproduct of the process of obtaining usable product from waste oil and oil shale.  PAO production became more viable when oil prices rose in the 1970’s.  Completely synthetic motor oils became available, but some sources say this product line had a couple of huge missteps that caused the whole synthetic market to go down in flames like a Zero with a punctured fuel tank.

Regardless, synthetics have been competing well in the marketplace for years now.  It’s useful to note that some synthetic oil is made from crude oil as a raw ingredient, but the crude oil is altered enough that it is essentially no longer oil.  Some synthetics have no crude oil whatsoever in their raw materials.  Pennzoil and Shell both offer synthetic oils made using natural gas as a base.

Synthetic Oil Advantages

• Higher Viscosity Index
• Better protection on cold starts
• Better performance at temperature extremes
• Better shear stability
• Better resistance to oxidation and sludge formation
• Extended drain/refill intervals
• Longer engine life, higher horsepower and improved fuel efficiency*

*I would put these claims in the category of “Needs data to substantiate specific claims”.  It depends on exactly what the claim is.  If someone said “10% longer engine life, 2% higher horsepower and 3% better mileage”, I would not be inclined to suspect those values.  But, it they were, say, 50%, 10% and 20%, I’d have to say “show me the data”.  You should also be aware that the term “fully synthetic” has no proper scientific definition and must be regarded as a marketing term.  Weird, huh?

American Petroleum Institute

The API has its roots in the years before World War One and was formed in 1919, several months after the war ended.  The API defines five groups of base oil.  Groups 1, 2 and 3 are mineral oils and groups 4 and 5 are synthetic.  Group 4 is PAO based and group 5 are base oils that don’t belong in the other four groups.

Fully synthetic oils are made from group 3 or group 4 base stock, or a mixture of the two. 

As a practical matter, these classifications are more a matter historic interest.  You are unlikely to have any SH from 1996 still kicking around and If it were me, I wouldn’t use it even if its classification was “Current”.  If it seems that the API classification changes every time you buy oil, now you know the whole story.

Synthetic Blend Oils

As the name implies, these are conventional mineral-based oils with synthetic oil added to them.  Base oil from groups 1, 2 and 3 are used to make synthetic blend oils. The goal was to create a product that had “synthetic like” performance, but with a lower price.  How successful were they?  Reasonably, it seems.  Synthetic blends account for a significant share of the market today.  The downside seems to be that the definition of “synthetic blend” hasn’t been standardized and it’s difficult to compare two products.  Perhaps the answer is to regard blends as somewhere between straight oils and synthetics, and expect them to be priced accordingly.  If the price of a blend is comparable to that of a fully synthetic, pass it by.

It’s worth noting that there is an enormous amount of money spent marketing oils, in part because it is so darn difficult to differentiate between them.  If you had a huge fleet of vehicles and kept meticulous service records, it might be possible to gain some insight into the performance of different oils, but that’s not most of us.  Even though you might gain insights, hard data would still be largely missing. .

Polyolesters were developed for turbine engines and for jet engines.  They are also used now for refrigeration and compressors.  Some companies, such as Red Line, manufacture a line of lubricants, including engine oil, that is polyolester based.

My conclusion about polyolester based oils is that they are likely well suited for specific applications where their huge shear strength is an advantage.  It seems that they aren’t ideal for “normal” daily use, with short trips and several months between oil changes.  If you are interested in this type of oil, I’d encourage you to do your own research.

How Often Should You Change Oil?

The old rule of thumb is 3 months, 3,000 miles, which today is obsolete.  I think the best advice is to follow the manufacturer’s recommendation for late model performance vehicles. For a vintage car, I’m comfortable in doing fall and spring oil changes. This may be too frequent by some standards, but it’s not grossly so, and it always brought me peace of mind.