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WHY ARE OIL CHANGES NECESSARY (OR -NOT- NECESSARY)?
I believe the whole point of using a premium synthetic oil is peace of mind. I like knowing that I can trust the oilin my car to protect my engine. I like knowing that 300,000 miles down the road, I won't necessarily have to start looking for another vehicle (unless I'M ready). I also like knowing that when 20,000 miles rolls around, I still have afew thousand miles left to find time to change the oil.
I used to be a pretty regular 3,000 mile oil changer. I had a very hard time believing that an oil could possiblylast longer than 5,000 or at best 7,000 miles. Changing at 3,000 miles was very safe and "assured" me of no mechanical breakdowns.
When I started looking at synthetics, my perspective changed a little. I figured, if I was going to go out and buy a $30,000 new car, I wanted to get the most for my money. Just protecting against breakdown for a couple hundred thousand miles wasn't enough. I don't take my car to the mechanic and hope he doesn't break it. I take my car to the mechanic so that he can make it better. The same can be true of your oil.
Let's talk about oil changes first. If it's necessary to change oil every 3,000 to 5,000 miles, then so be it. We should just do it, and accept that it's an integral part of keeping our vehicles from breaking down. But, if it's not necessary, why do it? Just because our Dad did? My Dad used to listen to 8-track tapes too. Now we've got these nifty little CD's that sound clear as a bell and last pretty much forever. Am I going to listen to 8-track tapes? Probably not. I don't change my oil every 3,000 miles anymore either.
WHY DO WE CHANGE OIL?
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.
OIL BREAKDOWN: WHAT REALLY CAUSES IT?
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 indefinitely with the right filtration system.As alluded to above, the first major difference between petroleum and synthetic oil is heat tolerance. 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 minimum to prevent possible high consumption.Today's engines are expected to put out more power from a smaller size and with less oil than engines of the past. Therefore, the engines run much hotter than they used to. That puts an increased burden on the oil. Even the best petroleum oils will have flash points only as high as 375 and 420 degrees F. For today's hot running engines, this may not be nearly enough protection. Just about any synthetic you come across will have a flash point over 430 degrees. High quality synthetics can have flash points over 450 degrees (Every AMSOIL synthetic oil has a flash point of over 450 degrees F with some exceeding 475 degrees). As a result, you will see little noticeable breakdown due to burn-off.
Just as important is the way in which petroleum and synthetic oils burn off. As a refined product, petroleum oils molecules are of varying sizes. Thus, as a petroleum oil heats up, the smaller molecules begin to burn off. Since the ash content in most petroleum oils is very high, deposits and sludge are left behind to coat the inside of your engine. 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, because they are not purified, but rather designed specifically from the ground up 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 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. 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.
As a side note (as it really has little bearing on when to change your oil), 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.
ADDITIVE DEPLETION?
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. Making a blanket statement that additives in oil die after only 2 to 3,000 miles is like saying that automobile tires will only last for 30,000 miles. To be sure, there are plenty of tires on the market that can only last for 30,000 miles, and then they're toast. But, there are many tires on the market nowadays that will last over 75,000 miles. The same scenario holds true for motor oils. Many oil companies are using the same additives in their oils as all of the other companies because they are cheap. That's why the oil costs less. You get what you pay for. If they were willing to spend the money on top-quality additive packages for their oils, every synthetic on the market would be recommended for extended drain intervals, and they would all be more expensive. The technology has been around for years. The problem is that oil companies make more money selling a cheaper grade oil and making sure that you change it more often. Mobil 1 is actually working on a 25,000 mile synthetic oil as we speak. They'll probably introduce it in the next couple of years.
Viscosity Retention -- Shear stable viscosity index improvers help AMSOIL 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.
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.
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 6 or 7 TBN. Many synthetic motor oils are formulated with 9-11 TBN. All AMSOIL synthetic oils (except the XL-7500) have TBN levels of 11 or better.
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