The Essential Guide to Motor Oils

By Roy Berndt
Program Manager
PROFormance Powertrain Products

Everyone that has the misfortune of having to purchase a new or remanufactured engine is keenly aware of the major expenditure and investment being made to have this complex collection of components replaced in your vehicle. Think of anything that you would purchase for thousands of dollars, be it new washer and dryer, a new sound system or perhaps an in home theater system. What about a new riding mower or snow blower, fishing boat or Jet Ski, you are hoping and praying that this will be an investment that will last for a long time. So you read the manuals and you make certain that you do all the things that should be done so that you get a long and trouble free pay back. Well engines need to be treated the same way and there is one thing above all things that is the most important of all things that you can do to insure that you have that long term investment payback. OIL! Oil is the life blood of an engine and if it becomes anemic (broken down) or contaminated with plaque (dirt or combustion contaminants) your engine will have a heart attack (catastrophic failure) and you have just lost your investment capitol that you made into your means of transportation.

There are only a few basic reasons why it is necessary to change your oil, and they all, in the end, have to do with decreased protection of your engine and decreased performance. If these elements can be minimized, then there would be little or no reason to change the oil.

First off, all oil breaks down. That generally will include basestocks and additives. Without focusing on performance characteristics, the most significant difference from one oil to another is how quickly breakdown occurs. Although there are many factors that contribute to the breakdown of an oil, heat is one of the most important. Depletion and decreased effectiveness of oil additives is also important, but that will be discussed later.

Petroleum oil begins to break-down almost immediately. A high quality synthetic, on the other hand, can last for many thousands of miles without any significant reduction in performance or protection characteristics. Synthetics designed from the right combination of basestocks and additives can last almost indefinitely with the right filtration system.

Flash point is the temperature at which an oil gives off vapors that can be ignited with a flame held over the oil. The lower the flash point the greater tendency for the oil to suffer vaporization loss at high temperatures and to burn off on hot cylinder walls and pistons.

The flash point can be an indicator of the quality of the base stock used. The higher the flash point the better. 400 degrees F is the absolute MINIMUM to prevent possible high consumption.

Even the best petroleum oils will have flash points only as high as 390 and 440 degrees F. Some actually have flashpoints as low as 350 degrees. For today's hot running engines, this is not nearly enough protection. Just

about any synthetic you come across will have a flashpoint over 440 degrees. Premium synthetics can have flashpoints over 450 degrees with some even reaching as high as 500 degrees. That's a big difference.

Thus, it becomes important to discuss the manner in which petroleum and synthetic oils burn off. As a refined product, petroleum oil molecules are of varying sizes. Thus, as a petroleum oil heats up, the smaller, lighter molecules begin to burn off first.

Since the ash content in many petroleum oils is higher than synthetics, deposits and sludge are left behind to coat the inside of your engine. Detergent and dispersant additives are used to keep these deposits to a minimum, but only so much can be done. Unless you're changing a petroleum oil every 2,000 to 3,000 miles some deposits are going to be left behind.

In addition, as smaller particles burn off, the larger, heavier molecules are all that is left to protect the engine. Unfortunately, these larger particles do not flow nearly as well and tend to blanket the components of your engine which only exacerbates the heat problem.

Synthetic oils, on the other hand, because they are not purified, but rather designed within a lab for lubrication purposes, are comprised of molecules of uniform size and shape. Therefore, even if a synthetic oil does burn a little, the remaining oil has the nearly the same chemical characteristics that it had before the burn off. There are no smaller molecules to burn-off and no heavier molecules to leave behind.

Moreover, many synthetics have very low ash content and little if any impurity. As a result, if oil burn-off does occur, there is little or no ash left behind to leave sludge and deposits on engine surfaces. Obviously, this leads to a cleaner burning, more fuel efficient engine.

Synthetics do a much better job of "cooling" engine components during operation. Because of their unique flow characteristics, engine components are likely to run 10 to 30 degrees cooler than with petroleum oils. This is important, because the hotter the components in your engine get, the more quickly they break down.

Most people understand that at cold temperatures, an oil tends to thicken up, and many people know that synthetics do a better job of staying fluid. However, many people don't realize why petroleum oils tend to thicken up. More importantly, though, they don't realize that this thickening process can wreak havoc on their oil. Because most petroleum oils contain paraffin (wax), they tend to thicken up considerably in cold temperatures. Therefore, in order to produce a petroleum oil that will perform adequately in severe cold temperatures, additives called pour point depressants must be used in high quantities. These additives are designed to keep the wax components of a petroleum oil from crystallizing. This maintains decent flow characteristics in cold weather for easier cold starts.

In areas where the temperature remains below zero for any period of time, these additives are used up very quickly because petroleum oils are so prone to wax crystallization. As a result, the oil begins to flow less easily in cold weather temperatures. Of course, the result is harder cold starts and tremendously increased engine wear. Thus, the oil must be changed in order to provide the cold weather engine protection which is necessary.

Synthetic oils, on the other hand, contain no paraffin. Therefore, they need NO pour point depressant additives. In addition, even without these additives, synthetics flow at far lower temperatures than petroleum oils. For instance, very few petroleum oils have pour points below -30 degrees F. Many synthetic oils, without any pour point depressants, have pour points below -50 degrees F. That's a big difference. There is, in fact, one oil on the market that has a pour point of -76 degrees F.

Since synthetics do not have any pour point depressants, there is no chance of these additives breaking down or being used up over time. There are no additives to break down. Therefore, synthetic oils maintain their cold temperature flow characteristics for a very long time. As a result, there is one less reason to change the oil if using synthetic as opposed to petroleum.

In addition, another part of cold weather driving that is extremely tough on an oil is condensation. Because it is so cold, it takes a fairly long drive to get the engine warm enough to burn off the condensation that occurs inside the engine. As a result, vehicles routinely driven short distances in cold weather will build up condensation within the oil. If left to do its dirty work, this water would cause acids to build up within the oil and corrosion would begin within your engine.

So, there are additives in the oil which are designed to combat these acids. Generally, the TBN value of an oil will be a good determination of how well and for how long an oil will be able to combat these acids. Most petroleum oils have TBN numbers around 5. Most synthetics have TBN levels over 8 or 9. Premium synthetic oils (especially those designed specifically for extended oil drains) will have TBN numbers around 11 to 14. This allows for much better acid control for a much longer period of time, thus decreasing the need for an oil change due to cold temperature condensation.

It is true that the additives in many oils begin breaking down after only a few thousand miles. What needs to be recognized is that there are different quality "grades" of additives just as there are different quality grades of just about any other product that you buy. There are also different combinations of additives that tend to work for better and for longer when combined than when used individually.

1. VISCOSITY RETENTION -- Shear stable viscosity index improvers help premium synthetic motor oils maintain their viscosity in the range appropriate to each grade over extended drain use. Conventional oils formulated with easily sheared viscosity index improvers often drop out of viscosity specification relatively quickly -- sometimes even before the end of a 3,000-mile oil drain interval. Viscosity loss leaves oils incapable of protecting engines from metal to metal contact and wear in high temperatures.

2. CONTAMINANT CONTROL -- Dispersants keep contaminants, including combustion by-products, suspended in oil. The rate of dispersant depletion depends on the motor oil's additive treat- rate and the oil's contaminant load. Premium synthetic motor oils are formulated with high additive treat rates specifically to allow extended drain intervals.

3. ACID CONTROL -- Total Base Number (TBN) describes the acid neutralization ability of an oil, with higher TBN oils providing longer lasting acid neutralization. Most passenger car motor oils are formulated with TBN of 5

to 7. Many synthetic motor oils are formulated with 9-11 TBN or higher. The result: longer and better acid neutralization capability allowing for extended drain use.

There is also the issue of contamination. Oil will be contaminated in three major ways.

One will be through debris that comes in through the air intake. Once it makes it through the air filter, it ends up in your oil. Once in your oil, it starts damaging your engine.

The second source of contamination will be metal shavings from the inside of your engine. The lesser the quality of the oil, the higher percentage of these shavings because there will be more metal to metal contact inside the engine.

The third source of contamination will be from combustion by- products. Combustion by-products will generally raise the acidity of your oil, which causes corrosion in your engine. In addition, they will be left behind as the engine oil burns off and will collect on the inside of your engine as deposits. To maintain the viability of your oil as well as protection of the engine, the contaminants have to be removed/neutralized.

One of the best ways to help with this process is to keep most of the contaminants from ever getting inside the engine in the first place. That's where your air filter comes in. Conventional paper air filters are pretty worthless. How many times have you removed your air filter for replacement only to find that you could write your name in the dust that collected around the air intake? That's just the stuff that was left behind. Imagine the amount that actually ended up inside the engine.

Part of the problem is that traditional paper filters do not fit all that snugly in the air intake compartment. They've improved, but they're still not great. More importantly, though, they let way too much debris shoot right through the filter element itself. As a side-note, they do not provide for very good air flow either.

You see, as a compromise to allow enough air flow for your engine to run "properly", surface type air filtration media have to allow certain sized particles to flow through. If they made the filtration media any more tightly woven, not enough air would pass through quickly enough to keep your vehicle running.

As a result, most paper filters won't catch anything smaller than about 20 to 40 microns with any real efficiency. In most cases, the more expensive the filter, the lower the micron level of filtration - and the lower the better, of course.

20 to 40 microns is pretty small. A human hair is about 100 microns in diameter. The problem is that 60% of engine wear is caused by particles between 5 and 20 microns (most likely because there is so much more of it). If you don't keep that stuff out, it'll eat away at your engine.

Ok, so we've taken care of the air intake, but what about metal particles from engine component wear? Well, there are a couple of things going on here that lead to better protection from a synthetic oil. One aspect that proves to be very important is cold weather starts.

The pour point of an oil is 5 degrees F above the point at which a chilled oil shows no movement at the surface for 5 seconds when inclined. That's tech-talk which basically means that the pour point of an oil is the point at which it ceases to be "pourable". This measurement is especially important for oils used in the winter.

A borderline pumping temperature is given by some manufacturers. This is the temperature at which the oil will pump and maintain "adequate" oil flow and pressure within an engine. This is not provided by a lot of the manufacturers, but generally seems to be about 20 degrees F above the pour point. So, the lower the pour point the better.

Most petroleum oils have pour points in the range of -15 to -35 degrees F. That means that their borderline pumping temperature is, at best, around -15 degrees F and probably closer to 5 to 10 degrees F. So, if you're running a petroleum oil, don't expect to go out and start your car at 0 degrees and have it purr like a kitten. It's going to spit and sputter and kick and scream for a few minutes.

Synthetic oils, on the other hand, routinely have pour points around -40 degrees or colder. Some have pour points as low as - 60 to -70 degrees F. Granted, there are very few of us who will ever have to start our car at this temperature, but imagine how well these oils lubricate at -20, if it they still flow at -70.

Generally, a thin film of synthetic oil will remain on engine components for days after it was last run. Petroleum oils tend to drain back down to the oil pan very quickly, leaving no oil film to protect your engine at start-up. Many auto techs and backyard mechnics can attest to this after doing engine tear- downs. Those using synthetic oil generally will have a thin film of oil left on components even if the engine has been sitting for awhile.

It's certainly not impenetrable, and I wouldn't go draining your oil after installing 6 quarts of synthetic just to see if your engine still runs, but it does serve a purpose. Your engine should virtually NEVER see metal to metal contact, whether in hot or cold climates. That's something that a petroleum oil can't do.

In addition, because of the higher film strength and better lubricity characteristics of synthetic oils, they routinely perform better on standardized ASTM wear scar tests. This would indicate a higher level of engine protection and would certainly lead to fewer engine wear particles in an engine. Hence, fewer contaminants in the oil to necessitate changing it.

Only one type of contaminant left to discuss: combustion by- products. These little buggers can wreak havoc in an engine. Not only can they form deposits on the inside of an engine which will rob it of performance and, ultimately, life expectancy, they will also tend to raise the acidity of the lubricant.

Higher acidity levels in your oil can lead to severe corrosion and break-down of engine components. In turn, this break-down leads to more oil contaminants and the necessity for an oil change.

Three things keep these contaminants in check: the TBN of the oil, high efficiency oil filtration and tight ring seal. The most important of these three is ring seal. If the number of combustion by-products entering your oil can be reduced, there will be less necessity to remove or neutralize them.

Poor ring seal allows combustion by-products to pass from the combustion chamber into the crankcase where they contaminate the oil. Tight ring seal keeps them out. Synthetic motor oils encourage a tighter ring seal than petroleum motor oils do.

As we discussed earlier, TBN (total base number) is a measure of how well a lubricant can neutralize acidic combustion by- products. The higher the TBN, the better the protection against these acidic by-products and the longer that protection will last. Hence, the possibility of longer oil drain intervals with oils that have high TBN values.

Oil filtration is the last component that must be discussed when making the case for extended oil drains. The next section in this series addresses this critical component.

First of all, the statistics previously mentioned regarding engine wear haven't changed. 60% of all engine wear is caused by particles between 5 and 20 microns. Unfortunately, most oil filters on the market today are lucky to remove even a small percentage of particles under 30 to 40 microns. This, again, leaves most of the harmful debris in your oil.

The actual filtration efficiency of a particular filter really depends upon the filter manufacturer, and it is sometimes very difficult to get any specific numbers from them regarding their filters' actual filtration efficiency.

So, most companies have gotten away from micron ratings (to avoid confusion) and have gone to an overall efficiency rating. In other words, an industry standard test is used in which oil is contaminated with a certain number of particles of varying micron sizes. At the end of the test, there is a measurement taken to determine the total percentage of ALL of these particles that were removed by the filter. That percentage is then stated as the overall filtration efficiency of the filter.

Some companies use a single pass test, others use a multiple pass test. Both are perfectly valid and will give you an excellent way of determining how well a filter will do its job, but you should not try to compare results from a single pass test to results of a multiple pass test. You'd be comparing apples and oranges. In either case, high efficiency filters will rank in the low to mid 90's for filtration efficiency. Off-the- shelf filters will rank in the mid 70's to mid 80's for filtration efficiency.

The fact is, you would probably be amazed at how much engine wear could be eliminated simply by using more advanced oil filtration. In paper 881825 the Society of Automotive Engineers indicates that a joint study was performed between AC Spark Plug and Detroit Diesel Corp. The study found that finer oil filtration significantly reduced the rate of engine wear.

According to the paper, the tests regarding engine wear within a diesel engine were performed using four levels of oil filtration. They chose filters whose efficiency rating was very high for particles of 40 micron, 15 micron, 8.5 micron and 7 micron sizes.

The same was done for gasoline engines, except that the relative sizes were 40 microns, 30 microns, 25 microns and 15 microns.

To make a long story short, the researchers had this to say:

"Abrasive engine wear can be substantially reduced with an increase in filter single pass efficiency. Compared to a 40 micron filter, engine wear was reduced by 50 percent with 30 micron filtration. Likewise, wear was reduced by 70 percent with 15 micron filtration."

By combining this type of oil filtration with the superior protection and cleanliness of a premium synthetic oil, you will virtually eliminate engine wear.

For those of you who just want to know what's best, here's a breakdown of the top 3, in based upon my findings. Mobil 1, Pure 1 and AMSOIL provide the greatest filtration efficiency in the tests results that I found. Mobil 1 and Pure 1 both achieved 93% overall filtration efficiency on the SAE HS806 test. AMSOIL scored a 94%.

In regards to filtration capacity, the AMSOIL outscored them by a wide margin. In a comparison of filters recommended for the same application, the AMSOIL could hold 21 grams of particulate matter. Comparable filters from Mobil 1 and Pure 1 held 18 grams and 15 grams respectively. So, the AMSOIL filter held 17% more than the Mobil 1 and 40% more than the Pure 1.

The AMSOIL company recommends changing their filters at 12,500 mile or 6 month increments. Based on their numbers, this seems reasonable. They have better capacity and stronger construction which should allow them to achieve longer change intervals. Since AMSOIL filters have been recommended for these intervals for about 20 years, it seems reasonable that they know what they're talking about.

Mobil 1 and Pure 1 recommend changing their filters at your vehicle manufacturer's recommendations. That generally means change the filter at each oil change which amounts to changing the filter every 3,000 to 7500 miles depending upon driving conditions. Because of the lower capacity of the Pure 1 filters, I'd recommend changing them closer to 3 to 5,000 miles. The Mobil 1 would probably last 5,000 to 7500 miles with good results.

As a side note, you can determine if your oil is bypassing your oil filter by touching your filter after at least 45 minutes to an hour's worth of driving. If the filter is hot, you're probably in good shape. If it's not, the oil is likely bypassing the filter, and it is time for a change.

This is probably way more information about oil that you would ever want to know but as you can see there are a lot of different ways that you can maximize the protection of your engine. The type of oil, oil filter and air filter can all be part of whether or not your engine is going to last a long trouble free time.