Thomas in Sweden wrote:
> Synthetic is made from mineral oil but with many refining stages
> before they add the different additives. In other words, they clean
> away the junk first. Some of these oils have more aggressive
> cleaners that eats away bad gaskets. Mobil 1 is reasonably safe to
> use in most "broken in" engines.
Wait a sec. First off synthoils come in two basic flavors, each of which is made
from different base materials and in different ways, but neither is based on
simple refined mineral oil. It is much, much more than simply cleaning the junk.
It's more like breaking the base down into its component molecules and selecting
out the molecules they want, then manufacturing a base stock with specific
molecules. Second, the additives in synthoils DO NOT eat gaskets, period!
Synthoils leak for many reasons, none of which has to do with the oil's ability
to destroy parts. In the old days the synthoils did not cause rubber to swell as
petroleum based oils did and many seals and rubber based gaskets would shrink
(as they will do if you allow an engine to sit for years) and this caused
leakage. But that issue was resolved 15-20 years ago. But at not time did
synthoils do any damage to any parts, including gaskets. The additive packages
in synthoils must meet the same specs and pass the same tests as any other oil,
so when you buy a grade of oil (SF or whatever) be it in petro or syntho, it
will meet the same strict requirements.