Which Engine Oil to Use
 

Hi, I currently own a 2.0 JDM WRX BUGEYE which is remapped to 350BHP.
I am gonna change the oil but not sure which grade to use due to power increase.

5w40, 10w40 or a 10w50 would all suffice as long as they were fully synthetic.

I'd go for Millers 10/40 CFS Fully syn for quality vs price.
Comes in 5 l. size which should give you enough extra oil between services if your engine is good.