Oil grade question?
 

When running synthetic, you guys running 5 - 30 or 10 - 30?

5-30

5-30 also

I run 5-20 because thats what Amsoil comes in. If you have high mileage and/or drive the car year round, you might want to step up to 10-30. I wouldnt run synthetic with a blower if I were you. You can get blow-by... You are better off running just a nice regular 5-30

I stick w/ Mobil 1 5W30 during the summer and 5W20 the rest of the time. Also, wouldn't you want to use synthetic for a blower since less oil evaporates as compared to conventional?

I don't believe oil evaporates.

Interesting point, but every single blower car built that I can think of uses synthetic right from the factory. Shit, in my turbo Saab it is all they allow.

Years ago there were fears about using synthetic in some cars because it was too thin. That was later refuted. Some say not to use it in high mileage cars for the same reasons.

Anyone else have a thought?

what gets me is, say your saab (or any other car w/synthetic being the "mandatory" oil) hits the 100,000 mile mark, are they going to tell you to put conventional oil in it then?

there is a nice right up in MM&FF from a long time dealer of Amsoil that talks on the various topics of the different synthetics for Amsoil & Mobil 1

Sept. Issue
Mustang Mail ~ Slippery Situation ~ Pg.32

I beleive the manual says to stick with syn. Also, they recomend changing it every 15k.....which is what I do.

5-20 which is what ford calls for. You dont need to change to regular fluide once your over 100k. If it had a small leak somewhere i might go with a thicker weight perhaps otherwise stick to what ford recomends. Its think because our motors are built tighter.

the viscosity is determined by the bearing surface clearances and use case. Our motors are pretty tight and do best with lighter weight oils unless you've race built the bottom end and you're going to put new bearings in every few runs... then you can use heavy race-only oils.

I use 5-20 or 5-30. There's no reason to go any heavier... it'll just increase oil pressures and decrease hp (pumping losses).

It's not so much that the oil itself evaporates but more so the impurity molecules in conventional oils since those molecules evaporate at a lower temp. Hence the reason why synthetics were first used in jet engines since the combination of heat and lower atmospheric pressures will cause conventional oil to evaporate more. That plus a jet engine obviously doesn't mix.