Sovi3t asked what oil I use in my personal SVX.
I use Mobile1 15W-50 oil.
I dragrace, autocross, and drive her pretty hard.
The viscosity of the oil is dependant on engine heat.
During startup is when most of engine wear occurs.
Synthetics were developed to flow well in very cold conditions.
When the engine is cold it's 15W, and flows well,
and when fully hot it flows as a 50W, giving maxium protection.
Sov13t has a manual transmission, and I believe LAN's chip.
He plans to dragrace his car.
He could see 7000+ rpm.
I would not want to spin a 13 (or 15) year old engine that fast on 10w-30.
Will a lower weight oil get better gas mileage, sure, but who cares!
He spent thousands of dollars installing a six speed trans in it, not to lower the cruising rpm, but to have fun!
Would I put 15W-50 in my dads Outback, nope.
I put in 10W-40 Mobile1.
Here is Mobile1s link.
http://www.mobiloil.com/USA-English/...1_15W-50_.aspx