synthetics and seals

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May 30, 2002
I don't fully understand POA, Esters ect. But as far as seal compatibility, which is desired, and which brands have them. I guess i just assumed a group III would tend to leak less than a true synthetic.
Out of Amsoil, Mobil 1, and group III's, which are better for an older(1995)vehicle?
The only one you really have to worry about are the Esters. An Ester is basically a material that is the product of an Acid/Alcohol reaction, a class of materials. As such there are many different individual types of Ester materials.

Some esters will cause seal materials like Neoprene and Buna-N to lose there elasticity or become brittle. In these applications a less reactive material usually a fluorocarbon such as Viton is used.

As for the automotive lubricants, I don't think many are formulated to incompatible with standard seal materials, like I say there are many different esters.
There is honestly no issue with seal leaking anymore unless you go back to the 70's vintage vehicles. PAO's shrink seals so therefore PAO bases like Mobil 1 use Estors which swells seals. So the net effect is to neutralize seal swelling/shrinkage. I believe Redline whi8ch is mostly an Ester uses an agent (not a PAO) to neutralize any seal problems. A group III needs nothing for seal deterioration (as far as I know-I could be wrong)

As far as your oil choices, Group III is not as good base as a PAO. But as far as seal deterioration in that year-its an non issue. Some folks have stated that you do tend to get more oil seeepage in a gasket which is already on the verge of leaking (with a PAO)
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