Originally posted by "Illswyn"
What items, please give examples, or any kind of information that shows that synthetic oils are inferior to petroleum oils. Any situation.
Aside from the case of pre-existing seal cracks, I can't think of any reason I wouldn't use synthetic in any car.
My experience
I used Mobil 1 syn almost exclusively on my stock engine. While I never burned any oil in stock form, on my Built engine it was a different story. My engine would go through sythetic like a child with a bag of candy.
Cast aluminum piston have a very very small metallic expansion rate under heat or (contraction?) under cold, meaning you will almost always have the same clearances in your cylinders.
Aftermarket Forged Pistons arent as nice in that sense. While they are stronger than the stock pistons, they expand more than the stock ones once they heat up, and contract more when they cool.
What does that mean? The clearances arent as tight with forged pistons. so running thin motor oil like mobil 1 syn, will cause you to burn oil on warm ups or possibly other situations.