Join Date: Nov 2002
Car 1: 1991 Legend L Sedan Wrecked!
Car 2: 95 Legend "L" Sedan
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Synthetic Oil Primer-- Good Reading
I came across this from a Honda accord forum written by Kit Sullivan. Very interesting reading
There are two types of lubrication that motor oil gives to your engine: The first type is called a Hydro-Static Boundary Layer, and that simply means that the viscosity of the oil, which is defined as resistance to flow, is what is causing the oil to cling to the inside surfaces of your engine, while the engine is turned off and the oil pump is not operating. When your engine is first started, this static layer of protection will give the engine adequate lubrication for a few minutes (5 or so) until the oil pump has the ability to create enough oil pressure to get the heated oil moving up into the upper parts of your motor.
At this point, the second type of lubrication takes over: The oil pump is forcing the moving oil in between the engine's internal components, creating what is called a Hydro-Dynamic Boundary Layer. That simply means oil that is moving around by way of the oil pump. With a single-grade oil, the heat from operation thins the oil that is clinging to the upper parts of the engine quickly, much more quickly than the oil in the pan. This reduces its viscosity, or ability to flow and causes the engine to lose its Hydro-Static Boundary Layer of lubrication. Unfortunately, the relatively thick single-grade 30-weight has not warmed up enough in the pan to be easily pumped up to the upper-engine before the static layer is depleted. So what you have is an engine that has lost its static lubrication, but is not receiving any adequate dynamic lubrication yet. This creates and abundance of wear and tear. This is why most engines from the 50's and 60's would be all used up at around 50,000-75,000 miles. That, and the high sulfur and phosphorous trace elements in the oil.
Multi-viscosity oil nearly perfectly solves this problem. By starting out at a relatively thin weight, such as 5 or 10, the oil will be very easily and quickly pumped up to the critical parts of the engine, creating the dynamic layer of protection long before the static layer of protection is gone. Through the use of man-made additives called Viscosity Index Improvers (long chain coil polymers, which are temperature-reactive), the oil will increase its viscosity as it heats up to its full operating temperature.
The operating temperature for motor oil is 150 degrees. This overlap of boundary layers of protection is what has enabled engines to go for 250,000-400,000 miles on a regular basis, along with much better refined oil. Basically, it has taken almost all of the wear and tear out of the warm-up phase of engine operation, which is where 75% of all internal engine wear comes from.
All is not perfect, however. The V.I Improvers are man-made additives and are VERY susceptible to the mechanical and very destructive shearing action of the engine. This shearing action actually tears apart the additive package, including the VI Improvers, after a certain amount of time. Driving habits, engine type and condition make an enormous difference in how long the additive package will function adequately, but 3 months-3,000 miles is a good rule of thumb for the typical city and highway driven vehicle. All city driving (stop and go, idling, etc...) will shorten the oils life dramatically by as much as 33%. Oil changes every 2,000 miles may not be excessive under those circumstances. On the other hand, mostly highway driving at relatively steady speeds on flat paved and dust-free roads is the best condition for your engine and its oil. This may allow you to increase the drain interval by as much as 50%.
The wider the range of viscosities on the oil, the less durable and resistant it is to Viscosity Index Breakdown. For example, 10W-30 oil does not have as much VI Improver as 5W-30, so there are fewer additives to be broken down by the shearing of the engine. In fact, 10W-30 is by far the most durable multi-vis oil there is. You should try to stay away from the wider spreads like 15W-50, 20W-50 and especially the 5W-50.
Also, thicker is not better, no matter what your mechanic or engineer told you. 20W-50 has 40% more viscosity (resistance to flow) at operating temperature than 10W-30. This means that your engine has to work 40% harder just to move the oil around inside your engine. An engine with thick oil produces significantly less power, uses more fuel, produces more emissions and runs hotter, all contributing to shorter engine life. A thinner oil can more easily and quickly be pumped-up to the critical parts of the engine, takes less energy to move it around, helps the engine to produce more power, less emissions, better economy. And the engine will last longer too! This has been proven numerous times in test after test, by many different and highly respected testing facilities.
Unfortunately, the rule that you can't teach an old dog new tricks prevents many 'experts' from accepting the facts. Indeed, when I was a kid, it was Castrol GTX 20W-50 in every car I had! In the years since, I have been working in the automotive lubrication industry, (15 years now) have been on the engineering boards of several major motor oil manufacturers. I feel lucky that I was able to see the light.
My '71 429 Mustang historically got about 10-11 mpg while it was run on 'dino' 20W-50. Now that I run nothing but Mobil 1 full synthetic in everything I own, my Mustang now gets about 17-18 mpg, and runs cooler to boot! That is significant. Unless your car is an actual bona fide 'RACE CAR'- no city driving, no idling, no stop and go traffic, no foul weather driving, etc...- do NOT use racing oil in your engine. Racing oil has a very narrow and specific additive package designs for engines that are used in racing situations, like constant high rpm operation, steady speeds, no stop and go, no foul weather, etc...
The oil that is designed for passenger cars is immensely more sophisticated than racing oil, only because it has to function under an almost impossible array of conditions. If you drive your car on the street most of the time, a good passenger car or maybe high performance oil will be much better for you than any racing oil.
The first number is the weight of the oil at cold start-up, so a lower number means a thinner oil that will be pumped up more readily.
The second number is the viscosity (sic) of the oil once it has reached operating temperature (150 degrees).
The additive 'V.I. Improver' helps it to do the opposite of what it wants to do when it warms up, which is thin out. (These types of oils are classified as 'non-Newtonian' because of this ability.)
5W-30 or 10W-30 is better in colder climes. In fact, the 'W' that is in the S.A.E. designation for an oils viscosity stands for winter, indicating that the oil will flow at its rated viscosity in 'winter driving conditions', as defined by the S.A.E. (By the way, the 'W' does not stand for weight, as many erroneously assume.)
Now, the first number in a multi-vis oil describes its viscometrics at cold start-up (engine off for 4 hours or longer, regardless of the outside ambient temperature). The second number describes it performance at operating temperature. This is where a lot of people get confused.
In a properly running engine with a properly functioning cooling system, it doesn't matter if you are driving in sub-zero temperature or 100 degree heat. The design of the cooling system will cause the engine & coolant, and therefore the oil to operate at whatever temperature it was designed to operate at. So what I'm saying is that the first number is critical in terms of climate. That is why the W (winter) designation is put after the first number, not at the end. The second number has almost no correlation to ambient temperature, only the regulated temperature of the engine.
A little trial and error will tell you exactly what weight of oil will best work in your car. For the first 500 or so miles after a fresh oil and filter change, the most volatile compounds of the motor oil will 'volitize' (boil off). This relatively rapid oil consumption will then taper off into the norm for that engine. So just top it off after 300-500 miles and then start the test:
Make sure that the oil is exactly on the full mark of your dipstick at the beginning of the test.
Check it at 500 miles, 1,000 miles and again at 1,500 miles.
Do not top it off at any time unless it falls dangerously low. (1 quart or more).
If you find that your engine is using oil at a faster rate than normal (1 quart/3,000 miles), then try using an oil with 10 viscosity points higher in the second number. As an example: start with 10W-30, and at 500 miles top it off. If 1,000 miles later you are a quart or half a quart low, record it and continue with the test. At 3,000 miles, if you have had to add more than a quart counting from the first 500 mile top-off, then you should use 10W-40 on the succeeding oil change.
Record your results again. If the 10W-40 does not volatize as readily then you should stick with that. However, if it still burns away, then try 20W-50. But, if the 10W-30 does NOT burn off too rapidly, then you should stick with that. No need to put thicker oil in if its serves no purpose right?
Of course, this is all assuming that your engine is in fairly sound operating condition. If your engine has worn or bad rings, or worn valve guides this test will not be conclusive. And if your choke is not adjusted correctly, you may get a large amount of unburned gasoline pumped into your oil, which is TERRIBLE for your engine. Fuel-diluted oil is one of the worst things that damage your engine. Gas is a solvent, and solvents cut the lubricity of oil-the exact opposite of what you want. If you can smell gas in your oil (on the dip stick), you are WAY past due for an oil change!
Only oils that are made using the 'PAO' method are truly considered to be synthetic. Castrol Synthetic Syntec is NOT synthetic oil. It is simply a 'Group II base stock' that has been further refined using propane de-waxing and severe hydro-treating to give a better base stock. But it is still refined from paraffinic crude, as all conventional 'dino' motor oil is. Although the US FTC allows Castrol to call it synthetic, it cannot be labeled as synthetic in Europe. It has a different name over there. Mobil 1, Sheaffers, and Royal Purple are all good synthetics. I stay away from Amsoil for reasons that are far too detailed. OK, I did not say that there was anything wrong with Amsoil. I just don't like for personal reasons, and I guess I'll explain why.
Most dino oils have about 20-25% additives, depending on viscosity and brand. But that figure is almost universal. Motor oil performs five functions in your engine:
Keeps a clean engine clean
As most already know, the crude is refined to whatever degree is financially reasonable, creating the base stocks. Then the additive package is introduced to further improve and modify the oils abilities. The major improvements in refining technologies over the years have produced very clean and high-quality base stocks, but that is still not enough. If you could somehow get a hold of motor oil with no additives (like those produced before 1961) and run it in your modern engine, your engine would self-destruct in a short amount of time. So additives are a very important part of the oil. Here's a shocker: The actual oil in your engine never wears out! It will always be oil.
There are 3 things that make motor oil unfit for continued use in an engine:
The additive package becomes depleted and can no longer offer all the performance and wear improvements necessary.
The oil becomes overly contaminated with particulate matter, combustion by-products, corrosive acids, dust, dirt, silica (VERY damaging!), and sludge. The sludge is a direct result of the combination of heat, air, water and petroleum (which is chemically the reactive trace elements left in the crude after refining: Sulfur and Phosphorous are the big ones).
The oil becomes fuel diluted with raw gasoline: gas does not lubricate, and an oil filter does not filter-out gas...it goes right through undeterred.
An oil filter is designed to filter out particulate matter only. Cars that are driven mainly in the city with a lot of low-speed driving, a lot of traffic lights, and do a lot of idling tend to put a lot more unburned gas into the oil. It is common for cars to burn a considerable amount of oil because it has become fuel diluted, reducing its ability to lubricate. Then, because the thinned-out oil cannot seal as well, it will let even more unburned fuel and contaminates past the rings, and more of the oil will burn away. The gas being introduced will sometimes take the place of the oil, and when you look on your dipstick, you see that it is full. This will lead some to believe that their car does not burn oil.
For example, say you take this car on a 75 mile highway trip and when you get there, you check the oil only to find out that it is 2 or more quarts low! This concerns you, because the car has never burned oil before. So you add a couple of quarts, putting good clean gasoline-free motor oil in its place with nice and new robust additives. You drive home the 75 miles at a little slower speeds because you are concerned about the oil loss. When you get home, you are fully expecting to see a 2 quart loss. But you are surprised to see that it is still on the full mark! So now you are confused. Many will blame the brand of oil, the shop who did the change by installing the cheapo house brand, and some will just scratch their heads in wonderment.
Fuel dilution is the culprit. In reality, the fresh oil helped to seal well, lubricate better and prevent excess oil loss. Highway driven cars are not nearly as susceptible to fuel-dilution problems, as the heat burns the dilution out of the oil.
So anyway, what I am saying is that it is the additive package that wears out, not the oil itself. Mobil 1 has about 10-12% additives, far less than 'dino' oil, because the synthetic base stocks are much, much closer to perfect and able to do an outstanding job without the use of nearly as many additives, which can be thought of as modifiers or band-aids. This higher percentage of actual OIL in the Mobil 1 formula lets the oil lubricate and cool your engine better. That is why engines that use a good synthetic get noticeably better mileage, run cooler, last longer, make more power, and produce fewer emissions. But to me, the most important reason that I use Mobil 1 is because there are no trace elements in it. None! Remember, it is the sulpher and phosphorous that helps lead to sludge formation in an engine. Without these trace elements in the oil, the formation of sludge is remarkably reduced. Engines that are run exclusively on Mobil 1 stay unbelievably clean and sludge-free. Sludge is far and away the leading cause of engine failure. That's why I don't like the Castrol synthetic product: It still contains many trace elements. Now Amsoil advertises that their oil is the extended drain interval oil. They do this by pumping up the additive package. They can have as much as 3 times as many additives as Mobil 1, so in theory it can take more shearing, lasting longer. More additives means less actual oil in the mix, resulting in less lubrication, less cooling, more wear and tear...you know the rest. The oil may last longer, but at what price? Your engine? That's not a good trade off for me. Don't get me wrong. Amsoil is a very good oil, but no matter how good any oil is, your engine is still going to produce contaminants and by-products, and the longer they are in your engine the more damage being done.
I have been involved with motor oil, oil manufacturing and testing, and additive technology for about 15 years or so. I spent a considerable amount of time at the Texaco lubrication and additive research and development facility in the Catskills, which was awesome. They have several fully computerized vehicle dynos there that can simulate any kind of driving environment. A few of the dynos are in sealed rooms, and they can add rain, snow sleet, blistering heat, rough terrain...just about anything you can imagine, all at the touch of a button from a separate control booth. These dynos run non-stop, 24 hours a day performing long-term evaluations. Pretty cool stuff, all in all.
There are a lot of things to consider when it comes to motor oil, to know the truth. There is so much detailed info to know that the oil companies know the average consumer would never put forth the effort to really understand oil, so they don't even try to sell it that way. They just come up with generic, 1-size-fits-all ad campaigns, so 'Joe Consumer' will stay just uneducated enough to think that there are really major differences between brands. In reality, as long as the oil has the API donut on the back label, nothing else really matters. The front label is totally worthless as far as a source of useful information. Most of the differences between brands is in the additive packages, and even then, the differences are relatively minute, as long as you are comparing similar types of oil from competing brands. The very best oil out there is not a whole lot better than the worst, as long as it meets the API and SAE classifications.
For all you guys out there that are looking to use some great oil at a great price... I have a shocker for you: The oil that Wal-Mart sells under their house name (Super-Tech) is very good quality oil. In many tests done over the last year or so, the Super-Tech oil was superior to many name-brand oils. The oil is supplied to Wal-Mart by Pennzoil/Quaker-State. It uses the same high-quality group II/III base stocks as their name oil, but uses an off-the shelf additive package. That doesn't mean it is lesser than the Z-7 or whatever additive package they advertise about. Update 10-01-05: While that was true at the time I wrote the article, it is not now. All of Wal-Mart's 'S/T/ oil is now supplied by 'Superior Lubricants' out of Louisiana. 'Superior' is an industrial refiner, and while they are a good place, they are not supplying the same quality base stocks as when QS/Pennzoil was. Consequently, the 'Super'Tech' full synthetic oil is now a 'Group III' base stock. While very good, it is not quite as sophisticated as a good Group IV or Group V PAO base stock. Most oil companies register their particular name brand additive package formulas, so they cannot be copied by another manufacturer. That way they can advertise about 'Nothing is the same as...' and all that kind of crap. An off the shelf package is available to whatever packager wants to buy it. So it is a little more economical for the packager. This also prevents stores like Pep Boys, Wal Mart etc...from advertising that their house oil is 'same as Q/S but at a cheaper price.' Wal-Mart's Super-Tech dino oil is less than a buck a quart, and their synthetic brand is $2.97/Qt. Great deal. Their Super-Tech oil filters are also very high quality, unfortunately much better than Fram. Fram has really gone downhill in the last several years, ever since Allied-Signal bought them. At less than $3.00 apiece, the S-T filters are a smokin' bargain. I use Mobil 1 in my real nice cars, and Super-Tech full synthetic in everything else. And I use Super-Tech filters on everything. I fully expect everyone who reads this to claim that I am full of beans (or something else!), and that I don't know what I am talking about. Actually, I do!
Assuming that your rebuilt engine is stock or close to it, I would use a good quality 10W-30 'dino' (conventional) oil until there is about 10-12,000 miles accumulated on the engine. There is a rather complicated reason for this, but not exactly the reason a lot of guys think. No matter how well the parts are manufactured, or how meticulous your engine builder is in maintaining his tolerances, the internals of your engine still have a lot of relatively rough friction surfaces when freshly put together. I'm talking about rings, cams, rockers, and bearings...stuff like that. There is a lot of processes manufacturers put their parts through to ensure that they have the desired hardness that is required for long life: Heat treating, Tuftriding, things like that.
For approximately the first 10-12,000 miles of a fresh engine's life, the parts all go through a combination of physical and molecular changes. First, there is a tremendous (relatively speaking) amount of friction on these surfaces for the first 12K, and the result is that the parts are reaching what engineers call equilibrium. The parts are wearing into a state of near perfect smoothness, in relation to each other. Much more perfectly smooth than any manufacturer could ever produce. Secondly, as this first 12K elapses the internal parts of the engine are also going through a molecular change (for want of a better word): the best hardening processes used by manufacturers cannot achieve what the constant heat and operation of 12K can put the parts through. The parts will become even more hardened, and much more resistant to wear and tear. But they also become more brittle.
For those reasons, it is vitally important that you operate your car in a variety of driving styles during this high-friction break-in period to ensure that the internals are fully worn-in, or seated by the time equilibrium sets in. If the parts are not fully worn-in by that time, then the new-found brittleness will cause an excess of wear and tear, shortening the engine's life. For that reason, it is a good idea to stick with regular 'dino' for the break-in period, so that you will have enough friction to wear in the parts, but not so much that you are damaging the engine. Since there is so much friction, and therefore much more microscopic (but still damaging!) particulate matter present in the oil, I would recommend changing it at the first 200 miles, then at 500 miles, and then every 1,000-1,500 miles until you have reached about 12K. At this point, you have done everything possible to help your engine reach as near a perfect state of equilibrium as possible, and no more break-in is necessary. That means that now you want to have as little internal friction as possible. At this point, switch to a good full synthetic.
Synthetic lubricates MUCH better than any conventional oil, which of course reduces internal friction. An engine that is properly broken in and in good operating condition, and with fresh fluids in it will suffer practically NO wear and tear for many thousands of miles. Synthetic also does not have any of the damaging trace elements in it (phosphorous, sulfur, etc...) that helps to create sludge and corrosive acids when combined with the by-products of combustion. The phosphorous, when combined with the remnants of the unburned hydro-carbons (gas), and then oxidized creates an acid that is chemically identical to battery acid. This most often leads to premature bearing failure and excessive cam wear. Since there is more actual oil in a full synthetic formula, there is more lubrication available to you. Plus, the relatively pure base stocks do not introduce any unwanted elements into your engine. 'P.A.O.' Synthesized oil is made of uniformly medium-sized molecules that all react in exactly a known fashion. The very small, highly volatile molecules that are present in 'dino' are what escape past the rings causing high oil consumption. This is known as volotizing.
There are additives in 'dino' that try to prevent this as much as possible. However, these all contribute to high consumption for the first 500 miles or so after an oil change as these light weight guys all quickly burn off. The very large, slow-moving paraffinic (wax) molecules in 'dino' are the ones that stick together at low temperature, thickening the oil and preventing it from being easily and quickly pumped to vital areas of the engine. By low temperature, I do not mean sub-zero. I'm talking about ambient temperature at 'cold start-up', even in 100 degree outside heat. Additives such as pour-point depressants are included to prevent this. At high temperatures, 'dino' oxidizes extremely rapidly. The oil absorbs oxygen right out of the air. Oxidized oil does not lubricate well, in fact it is thick and gooey, just the opposite of what we want, right? Keeping your oil at a reasonable operating temperature is vitally important to prevent oxidation, for at low temperatures, oil is almost totally resistant to oxidation. Higher capacities and oil coolers are both excellent ways to accomplish this, as most already know. All of these things happening in unison often create a common situation: Oil is used for too long a period and is exposed to extreme heat for too long a period and becomes overly oxidized, dramatically raising its viscosity. What started as relatively light weight 10W-30 may now be a straight 50 weight, all thick, sticky and gooey. This creates less-than-acceptable sealing performance from the oil, therefore allowing an excess of combustion by-products to 'blow-by' the rings into the crankcase. This blow-by introduces unburned fuel into the oil an accelerated rate, and since gas is a solvent, it cuts the lubricity of the thick, overly-oxidized oil down to maybe a straight 30 or 40 weight. So when an average consumer hears that Ford claims his new car can go 7,500 miles between oil changes, and 15,000 miles between filter changes, he checks the oil frequently to make sure that the level and condition are adequate. Lets say he checks at 5,000 miles and finds the level acceptable, doesn't seem too dark or sticky, and assumes that Ford now makes better engines. Wow! In reality, what he was looking at was heavily oxidized and fuel diluted oil. The fuel dilution causes the old oil to feel thin and 'oily', not sticky, Plus it gives it a somewhat lighter color, fooling him. The gas, of course, prevents proper lubrication, increasing wear and tear. Additionally, the additive package is all but totally depleted by now, offering none of the long term benefits of clean oil. Fortunately, ALL of these terrible things can be totally avoided with frequent oil and filter changes!
A Word About Synthetics
Only oils that are created using Poly-Alpha-Olephin based technology are considered to be synthetic. At least by anyone who knows better. The Castrol Syntec synthetic oil is actually just a much more thoroughly refined 'dino', coming from the same crude that all conventional 'dinos' come from. Even though their base stocks closely approach the performance of PAO synthetics, they still contain trace elements, and are still susceptible to the effects of temperature extremes that full synthetics are almost immune to. By the way, Castrol does not make their own oil. They never have. They don't even own a single refinery. Never have. They simply but their base stocks from one of the commercial suppliers (Coastal-Unilube is one), buy a custom-blended additive package from an additive supplier, and have a bottler package and label it all for them. That doesn't mean that it isn't any good. It is very good. But in repeated testing, the Castrol products exhibit a wide variance in performance, the results of getting their products from many different suppliers. Syntec may be good, even excellent oil...but it sure ain't synthetic! The same was true for Texaco Havoline oil for a couple of years - two separate companies were legally allowed to manufacture and distribute Havoline oil. Shell was one, Equilon was the other. The Equilon-sourced product was far superior to the Shell-sourced product in every single performance category in repeated tests. Unfortunately, there was no way for the average consumer to determine which supplier his Havoline was coming from, for the labels were quickly changed to remove this information. This is all a moot point now for Shell is the sole supplier of Havoline branded oil now. I just stick with Mobil 1, and that other stuff I talked about earlier.
Porsche, along with most other European manufacturers typically recommend extended drain intervals, such as the 15,000 mile interval that you are talking about. Driving conditions and the typical driver's habits are markedly different from those in America. The bulk of driving conditions in Europe is on high-speed highways, with a small amount of city-type driving. This is the best driving conditions for oil and therefore an engine. American driving typically consists mostly of city and traffic-jam driving which is the absolute worst kind of driving. That is why American manufacturers are slow to come around the same extended length oil drain intervals as their European counterparts. But they are coming around. The extended drain interval also allows manufacturers to advertise a lower maintenance cost to the consumer, which is a powerful sales tool. Of course, these are under ideal normal driving conditions, which are almost totally non-existent in reality. That's why there are always severe driving schedules, or a 'B' schedule in most owner's manuals.
As far as the Porsche's engine using higher quality components and manufacturing? You bet they do! What do you think you are paying for? But that doesn't mean that they are indestructible. Remember, when a manufacturer says "Change your oil every 15,000 miles", they are not claiming that the car's engine will last indefinitely. They are only claiming that the engine will give good service for the length of the warranty period. These are usually anywhere from 36,000 to 100,000 miles, but rarely more than that. Any major problems beyond this point and you are on your own, baby! But with today's technology and manufacturing methods, ANY engine, even the lowliest Daewoo or Kia should be able to give good service for 100,000 miles. It just takes maintenance. 15,000 mile drain intervals will allow an acceptable amount of wear and tear that will not show up in any appreciable way for the length of the warranty. The key here is that there IS unnecessary wear and tear being introduced with these extended intervals. What I believe and try to teach my employees and customers is that with a properly broken-in engine, regular maintenance( 3,000 mile oil changes) and sensible driving habits, it is very possible to have an engine that basically suffers NO wear and tear for many, many thousands of miles. The rate of wear can be slowed down to such a degree that it is almost non-existent.
My own personal experience has borne this out time and time again. My 79 Lincoln MK-V (400 2-V) has over 340,000 miles on the original engine and runs perfect. No leaks, knocks or noises. Does not burn oil. And since these engines are known for being underpowered and thirsty, but certainly NOT known for being durable...this is really a testament. 3,000 mile oil changes are recommended for the sake of preventing wear and tear. 15,000 mile oil changes are recommended for the sake of slowing down the wear and tear. Another consideration for the manufacturers is that the various world governments are urging them to use less and less oil products whenever possible. The extended drain intervals are one way to help achieve that.
The problem we are all facing is the upcoming adoption of the new 'GF-4' classification of motor oil. The A.P.I. (American Petroleum Institute) adopted a classification system to rate the performance of motor oil back in 1961. For gasoline burning engines, it uses letters and the first letter is always an 'S', signifying that it is for 'Service Stations' (remember those?), assuming that a service station would only be adding oil to gas-burning engines, since no one ever believed there would be diesel powered cars at that time. I always found it easier to think of the 'S' as standing for spark ignition, which is how a gas engine works. Anyway, the first letter is 'S', and the second letter denotes the performance characteristics of the oil through the use of additives. 'SA' oil was introduced in 1961. Every time the oils required performance was improved, the second letter was advanced. We are currently at a level of 'SL' for new vehicles sold today. This is a superseding system, meaning that every newer performance-grade oil can be used in any application that called for a lesser grade. e.g. today's 'SL' rated oil can be used in a 1995 vehicle that originally called for an 'SG' rated oil. And that older car will derive extra benefits from the newer oil that were not available when the car was new. However, an older 'SG' rated oil CANNOT be used in today's cars that require an 'SL' rated oil.
By the way, it is highly unlikely that anyone would ever be able to accidentally find or buy any outdated motor oil considering that motor oil is a fast moving commodity. It just doesn't sit on the shelves for too long! The government requirements of upcoming oils performance are so stringent that simply improving the existing formulations will not be sufficient. The main culprit is phosphorous. The phosphorous content in motor oil and gasoline is the main contributor to catalytic converter failure. Today's requirements are that a properly maintained catalytic converter must perform within its design parameters for a minimum of 50,000 miles, and they are designed to do so. When this requirement was put into effect (1974), vehicles lasted an average of 75,000 miles or so. The idea was that as most of the cars converter's started to fail, they would be heading to the junkyard anyway. With today's vehicles traveling 200,000 miles regularly, the government feels that the 50,000 mile minimum is inadequate for long-term protection of the environment. So they raised it to 150,000 miles, beginning with the 2005 model year. The only way that this is possible is for the phosphorous content in motor oil to be reduced by 50% from what it is currently. The problem is that it is not possible to refine conventional 'dino' oil using the methods that are currently in use by refineries and make oil that is sufficient for this. It must be refined using a different method, (read: expensive) and the big problem is that neither one of these oils will be compatible with the opposite vehicle's applications. That means that there will be 2 totally different type of oils for the consumer to choose from. Well, the oil and vehicle manufacturer's have lobbied hard, and have won a small concession: Instead of 'GF-4' having 50% of the current levels of phosphorous, current refining methods can reduce it by about 30% maximum, although it will still cost more. The benefit however, is that it will be compatible with all standard 'API' as well as 'GF' classifications. So one type of oil can satisfy both standards. This will only be short-lived, however, as part of the agreement for the 30% reduction for 2005, is that by 2008 'GF-5' will be the requirement at the original 50% reduction. Whereas the API set the standards for American vehicles performance, and the European and Japanese counterparts set their standards, this is the first time that all three of these organizations have gotten together to set a world standard. This 'world' organization is called 'ILSAC' (International Lubrication Standardization Acceptance Committee), and you will see this on the back of almost all current motor oils.
The oil companies found out that by adding a small amount of synthetic base stock to conventional 'dino' stock, they were able to significantly increase its cold and hot temperature performance. It approaches full-synthetic performance, but is still a ways away. (Blended oils are almost a definite with GF-4/5 oils). They are significantly better than regular 'dino'. However, there are still the trace elements in the 'dino' portion of the oil, and that is what contributes to sludge formation. For that reason, I do not use blended oils. Blended oils use anywhere from 2% to %5 synthetic base, depending on viscosity and brand. None are higher than 5%. (Most erroneously assume it is 50/50). This is a BIG moneymaker for the oil companies.
If there were insufficient boundary layers of lubrication between the gears in a diff or a manual tranny, then the internals of the gearbox would weld themselves together relatively quickly. That's no good. So there is a complex group of additives to address just this predicament, and it is called E.P. The additives that make up E.P. (which stands for extreme pressure) are developed from zinc, copper, brass, and other chlorinated solvents. These are commonly referred to as the 'yellow metals', and they possess some very desirable properties: they have a very low coefficient of friction, and they tend to stay-put, which makes them very resistant to the gearbox's attempts to remove them from contact surfaces through the mechanical shearing action of the component in question. Basically, no matter how much pressure is applied to these additives, they cannot be squeezed out from between the contact surfaces. This is what allows gear oils to lubricate so effectively without any type of Hydro-Dynamic protection.
This may bring up a couple of questions amongst the more curious: First, if E.P. is that good, how come it isn't put in motor oil to provide even better protection when the engine is first started, or if you were suddenly to lose oil pressure?
Great idea, but it can't work for a couple of reasons.
Mostly because it is not legal for the additive to be put in motor oil, because chlorine and any chlorinated solvent or derivative is considered to be a carcinogen, so it can't be in there. The thinking is that a portion will escape to the atmosphere through normal combustion and exhaust, and the government says no!
Transmissions and gearboxes are considered to be sealed, so the same rules do not apply. Also, when a chlorinated compound is combined with the normal by-products of combustion, it creates an acid that is almost chemically identical to battery acid! This wreaks havoc with bearings and such. In fact, before this was illegal, there were chlorine-based additives in motor oil, and they had a terrible effect on engines. That is why most engines in the 50's and 60's would give good service for about 60-75,000 miles, and at that point they would be smokers and knockers. Basically, landfill material. (By the way, it is not legal for the manufacturers to put EP in the oil, but there is no law that says YOU can't put it in your own oil, if you would ever want to.)
EP is the active ingredient (hidden through clever chemical copyrights on the labels) in many engine treatments available out there. Specifically, Dura-Lube is loaded with it. Stay away from that stuff. Or, if you use it, just make sure you change your oil at least every 3 months regardless of the miles! At least that will keep the harmful acids from forming so quickly. Did you ever wonder why Slick 50 or one of the other engine treatment companies didn't market their own brand of motor oil with their product built right in? Well, because they are not legally allowed to. Slick 50 tried to get away with selling oil filters with the product already installed, but they had to pull those from the market pretty quickly.
So, as long as the gear oil you are using is of the correct viscosity range, has the correct EP and LS (limited slip) additives in it, then synthetic is in all respects a better choice than any 'dino' lubricant.
Kit Sullivan is a15+ year automotive lubrication engineer and a classic and muscle car enthusiast and collector