I know this has been covered many times but I keep getting told different. Ive a 03 wrx its pretty standard and would get fast road use, no track. The manual says to use 5w/30 but everyone seems to recommend 5w/40. Ive also been told 5w is too thin for a boxer engine. It has a full subaru history and they always used 10w/40 semi. Could someone please tell me if a 5w is ok or is it best with a 10w? Cheers stu.

 

a new-age WRX with no extreme mods or track use will be perfectly fine with a high quality 5w40.............

aggressive driving style/use then you'd be better with the likes of a 10w50

 

Cheers.