has anyone used 5-50 in tehre redtops?

[crazy9ceguy]

is 5-50 bad to use for sr20 redtops?

[DuffMan]

Is this castrol syntec 5w50? It's fine for SRs.

[crazy9ceguy]

which one is better castrol 5w50 or mobil 1 15w50?

[DuffMan]

They are rated at the same weight and test the same viscosity at 100 degrees celcius so they should be equal in terms of how well they protect the engine.

The Castrol is a better cold weather oil, because it wont be as thick at low temps. However, I would assume to get 5w50 would require more viscosity modifiers. This means the Castrol will break down over time and offer less protection at high temp if it has been in the car for a while, and probably should be changed more frequently.