Quote:
Originally Posted by FRSRAVEN
If you track the car, then choose an oil to match. Even then, the primary concern is viscosity. Toyota/Subaru specified roughly a 5.2-9.3cSt (20 weight) oil for this engine, so choose an oil that will fall within these specifications at the oil temperatures you are likely to see. For a street car, this would be your average 20 weight oil. If you track the car, and see higher oil temperatures, you'll probably need to step up to a 30 weight or even a 40 weight oil.
A 40 weight oil at 212 degrees F (common temperature on the "street") will be around 14cSt. This same oil at 266 degrees F (common temperature on the "track") will be around 8cSt.
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Interesting logic. It's probably also worth mentioning the viscosity at start-up. At 60F, a 5W-40 will be approximately 100 centiStokes thicker than a 0W-20.
If the temp is 50F, the 5W-40 will be approximately 180 centiStokes thicker than a 0W-20. My figures are based on using Castrol Edge 0W-20 and 5W-40 and a viscosity calculator.
I would not go with a 40 grade oil on stock internals no matter what the conditions.
-Dennis