Engine Oils

The life blood of any engine is the oil that flows through it. Change that oil every 3000 miles and you’ll have a reliable engine.

We all have heard this from the very first day that we were exposed to internal combustion engines. Our fathers heard it from their fathers and we heard it from ours. That has always been the truth and still is today. The fact is that oil, both conventional and synthetic start to break down as soon as you crank the engine after the oil is changed. Pressure and heat, burnt and unburned gases combine in the crank case and become an acid that slowly eats away at the internal parts of the engine, especially the bearings. Ever notice how different any engine sounds when you first crank it after changing its oil? Especially if you have went a little long on that last oil change.

In General
There are so many brands, both conventional and synthetic. Which is best for your particular application? Perhaps some information on the difference between conventional and synthetic oils will assist you in making that decision.

All engine oils begin with a highly refined base oil that has additives that enhance lubrication and additives that help to prevent the oil from breaking down. The base oil is the major difference between conventional and synthetic oils.

All engine oils have to battle the same enemies inside an engine:

1. Loss of lubrication. The primarily job of any motor oil is to provide a cushion between various metal parts in the engine. This cushion of oil is just microns thick and it is crucial that it be maintained. Various additives in the oils are used to help maintain this cushion. As the oil gets hot and as the oil ages, this oil cushion gets harder to maintain.

2. Sludge and varnish. As engine oil gets hot, especially if the heat is out of the oil’s operating range, both sludge and varnish are produced. Varnish coats itself on metal parts and interferes with the actual oil itself contacting the metal and producing the cushion. Sludge forms and actually can clog the internal oil passages to various parts of the engine preventing oil from even reaching those areas. Both are bad for any engine. Usually if the oil hasn’t been changed in a very long time or if the engine was ran hot are good signs of these 2.

3. Viscosity. As any oil ages it looses viscosity. Viscosity is a measurement of the oil’s weight. To much is just as bad as to little. Multiweight oils were introduced for this reason. Lower weights for when the engine is initially started especially in cold weather and higher weights for after the engine reaches optimum running temp. Some folks run a single weight oil that is midrange. All oils loose viscosity as they are used. This is why it is important to change them on a regular schedule.

Once a conventional motor oil has reached its upper limit, the valuable oil additives can cook out of the oil and you are then back to just plain old, dirty, burnt, gas laden oil. Not too good for your engine. This is where the 3000 mile oil change came into being. It is around about this time that the oil’s viscosity has broken down, the oil additives are diminished and the oil isn’t providing the level of protection to your engine that it really needs.

The next time that you change your oil, notice the smell of the oil. Smells a little burnt?. Heat is what destroys any motor oil. It can occur all at one time like an engine overheating, or over time like between oil changes. The result is the same. Dirty, burnt engine oil that needs to be changed.

Conventional Oils
Conventional oil is still what most people have in their engines today. Primarily its the low cost of a quart of conventional oil versus the cost of a quart of synthetic oil that keeps conventional oil in the majority of engines.

During the refining process conventional motor oils receive additives that are designed to produce certain results from the motor oil. Detergents are added to clean the varnish from the engine, anti-foaming agents are added to keep the oil from foaming at high heat, viscosity stabilizers to assist in maintaining the oil’s viscosity, etc. Petroleum engineers have been able to produce some very high quality conventional motor oils by highly managing the refining process with these additives.

However even with a highly refined base oil and additives conventional motor oils are limited in what they can achieve. The conventional base oil molecular structure has molecules of various sizes along with impurities. Somewhere in that base oil is a molecular structure that is of the optimum size that provides the best lubrication.

Synthetic Oils
Synthetic petroleum products have been around for some time. During WWII the Germans produced synthetic fuels from coal when their regular supplies of crude oil were distributed by Allied bombing raids. They discovered that they could engineer crude oil in addition to just refining it.

Synthetic oil is produced much the same as conventional oil, having both a base oil and the various additives. However in synthetic oils the base oil itself is synthesized. This is the major difference between conventional and synthetic oils and why synthetics have such an advantage over conventional oils.

While the synthetic base oil is being synthesized its molecular structure is engineered to produce a molecule of a specific and consistent size. The ideal molecule size is isolated and the result is a pure base oil free of the various impurities that cause the varnishing and sludging that is associated with conventional oils.

The synthetic oil base along with its associated additives results in an oil that could reach both lower and higher temps and still maintain its superior lubrication properties over a much longer period of time.

1. Improved lubrication. Due to the fact that the oil molecules are modified in synthetic oils, they can be made to flow into areas where conventional oils just cant go. They can maintain that oil cushion a lot longer under harsher engine conditions.

2. Reduced sludge and varnish. Synthetic oils have been engineered to run throughout a much broader temp range. Whereas a conventional oil might start to sludge and varnish at its upper temp range, a synthetic will not be affected due to its engineered base oil.

3. Viscosity. Because the base oil is synthesized the molecule size has been optimized for proper viscosity.

What about blended oils?
Blended oils are exactly that. They are better than a regular conventional oil but don't give the superior performance of a fully synthetic oil.

You can do your own blended oil. Just make sure that you stay with the same oil brand. Motor oils from the leading motor oil producers have their own specific base oils and additives. Nearly every oil that you see says that it is compatible with other oils but you for sure will get the best performance if you stay with the same oil brands if you ever mix oils in your engine.


My Own Experience with Synthetic Oil
My first experience with synthetic oils was with my 1991 Chevy S10 extended cab 4x4. I bought it brand new in 1991 and on my first oil change I put in Mobil One. I had seen the commercials on the tube and I had just recently lost an engine in my car due to a failed oil pump. The oil pump was stopped up with sludge. I wanted to see if I could help prevent this with my new truck.

On each and every oil change at 5000 miles I ponied up the extra bucks for the oil and continued to use Mobil One until Castrol Syntec came out. I had ran Castrol GTX in a 1978 Datsun 280Z that I once had and I like that Castrol oil so I tried Syntec. Castrol Syntec is what I ran in my S10 till the right head gasket let go at 110,000.

I could have just had that right head gasket replaced and when ahead with another 100,000. However I have always wanted more power from my trusty ole 1991 4.3L engine so I decided to have the engine torn down, and do a custom buildup. That buildup is covered in another article on this website.

As the engine was torn down I got to see if paying the bucks for all those many quarts of synthetic oil had paid off. I got to see what 110,000 miles looks like on an engine that been ran with nothing but synthetic oils.

* All of the cylinders mic'd to within the limits on the factory spec for the cylinders.
* The oil pan. After the oil was drained and the oil pan was dropped there was nothing in it but some oil. No sludge and the oil pump pickup was clean.
* All the bearings were in great shape. It was obvious they had received superior lubrication.
* The overall condition of the engine was that it was very clean inside.
* Instead of an engine with over 110,000 miles on it, this engine looked as if it had half or maybe a third of those miles on it.

I remember hearing this from the master mechanic that did the buildup on my engine. Whatever you did with that engine, you need to do it again with the built-up engine. That has to be the cleanest engine at 110,000 miles that I have ever seen. By the way, my other vehicle is a 1996 Chevy ImpalaSS. Needless to say the first time that I got to change the oil in went the Castrol Syntec. 5W-30. I noticed the difference during the next extended trip that I took in the car.

Conclusions
There are several that can be made about conventional and synthetic oils. Without any doubt the extra money that a quart of synthetic oil costs is well worth it in the long run. The 3,000 mile oil change is pretty much history with the synthetics and the free flowing characteristics of synthetics provides for superior lubrication.

When an engine that has had nothing but conventional oils in it is changed over to synthetic you might get some oil leakage at the seals. This is due to those engineered molecules flowing into areas that the conventional oils cant reach and the detergent additives cleaning up the varnish. If the engine seals are in otherwise good shape and the engine doesn’t have a lot of miles on it the seals will reseal. This happened with me and my ImpalaSS. It wasn’t a bad leak, but I could see the oil around the front main engine seal. I cleaned it off and kept a good check on it The next oil change the leak was gone.

One reason to for sure run a conventional oil. During the break-in of a new engine or a freshly built-up engine nothing but a high grade conventional oil should be used. The new engine parts need a certain amount of friction in order to seat themselves i.e. valves, and the free flowing synthetics don't allow enough of the required friction. After the break-in, go with your choice of synthetic oil.

Just change that oil and remember to use a good oil filter too. Your engine deserves it!

Last Modified: 7-13-05 JCH