Have been told it flows thiner than the Mobil 1 pure synthetic 5w20 I usually run thus should go up a step in weight to maybe 5w30. Obviously I want good performance and economy but don't want to be consuming oil with my 80k engine because it's flowing as thin as water. Thx alot.

 

^ A '99 GT should call for 5W-30. Amsoil 0W or 5W-30 would work well. 5W-20 oil will not hurt it, but I do not see the need to run it.

 

Without seeing the specs of both oils I can't say which is a "lighter" oil. Both should be very similar since they're both 20 weight.

I'd run 5w-30. Added protection over 5w-20 while the MPG and "performance" difference would go unnoticed.

EDIT: After looking at the spec M1 and Amsoil 5w-20 are very similar oil. You wouldn't notice a difference.

 

I would never run a 5w20, thats all for gas mileage propaganda.

 

ain't CAFE laws a bitch!

 

My Mazda3 has 78K on it and I have been running 5w20 but I believe I could go with 5w30, thoughts?

 

Fred without a doubt run 5w30, all vehicle that spec 5w20 is for cafe laws and gas mileage claims. The same motors in the united states that spec 5w20 spec 30w in other countries.

 

do any retail stores carry amsoil

 

Some do, but not very easy to find. It's easier to buy it direct from Amsoil at dealer cost by signing up as a preferred customer.

 

Gonna go with the 5w30 for the MZ3 then