Synthetic Oil and other comments

Posted by Joe on Sep. 23, 1998 at 08:05:41

In Reply to: More on Motor Oil - Long
posted by Bobby Crumpley on Sep. 22, 1998 at 10:48:49

: Gordon asked in his last post about using synthetic oils.Well, if it were MY new engine (and it will be soon), I would use NOTHING BUT synthetic oil from the first fire of the engine.We can talk more about that if anyone is interested...Sorry to ramble on for so long!
: Thanks,
: Bobby
Bobby and others
The advantage of synthetic oil is in that the oil is "engineered" to have a very "flat" viscosity curve, i.e. the viscosity at elevated temperatures is only a bit less than the viscosity at room temperature.
This is the reason why synthetic oils generally perform better at slightly lower SAE grades for service and easier starting under winter conditions.And also one reason why the newer cars are tending to go to the 5W family of oils.
Although it is not generally said (In marketing you have to have *something* to differentiate your high end, high profit product), I suspect that even the common grades of oil now contain some percentage of synthetic oil.Viscosity curves of even ordinary oils have been getting flatter and flatter for years as the science and art of refining and blending have improved.Some of this improvement is no doubt due to mixing of oilstocks.Also, another reason why 5W oils are becoming more common: carmakers can now predict and rely on high end performance of the commonly available oil in their engines.
Also, I like to think that the properties of the synthetic oil are optimised to be as "slippery" as possible, although some will tell you that this is not always desirable as in the case of sliding friction of piston rings against cylinder walls.Hence the usual warnings against using a pure synthetic oil until the engine is past the "break in" period when a little wear is desired and encouraged.
In today's marketplace for Model A's I'm not sure I would go to the additional expense of a pure synthetic oil.Model A engines are being rebuilt regularly and even NOS parts are available. A rare Mercedes or Rolls Royce or the remaining two Curtiss Jenny Airplanes (one found built into a building!) are a different matter.In that case operation with anything less than a synthetic oil would be a crime. (Actually, in that case, operation of any sort is a crime since operational wear is inevitable no matter the oil.)
For these exceptional cases, financial considerations are secondary.If your only criteria is to preserve and protect the restored engine, a synthetic oil is the way to go.It will result in the maximum engine life and conserve engine metal.
With the finance aspect considered, the additional cost of a synthetic oil must be balanced against the cost of an eventual engine rebuild.I admit the tendency generally today is to come closer to a financial justification for using synthetic oils.Synthetic oils are becoming cheaper and engine rebuilds are becoming more expensive.
I think the Model A engine is probably about "mid-way" in this justification since at about $1500 for a rebuilt unit it seems about average to what it takes to replace an automobile engine today.As with our common everyday cars, I suspect if you buy a high quality commonly available "non-synthetic" oil for your Model A you will probably do about the best you can on payback and make a reasonable effort at lengthening the life of your "A".
It's certainly a better oil than it was originally designed for.
Hope this helps,
Joe