quote:
Originally posted by Oz_Mick:
I own two turbo Subarus and for both they recommend 5W30. In the WRX I run 10W40 because the car does a lot of trackwork in the heat of summer. I've seen more than one car running 5W30 in summer on the track that did its bearings.
I remember reading a few years ago, on a Subaru enthusiast's forum from the UK, about rod and main bearing failures in WRX's. This was happening somewhat frequently to owners in both the UK and in OZ. This occurred most often during high speed, very high rpm throttle lift. It seemed that the only thing that prevented this with any degree of consistency was switching to a thicker (5w40 or 10w40) high quality synthetic oil. As I recall Motul was the specific brand.
Apparently the thinner oils had insufficient film strength under these conditions and the shock to the bearings from the high rpm throttle lift would cause the bearings to scuff and fail.