Using 0-40W will do no harm what so ever to your engine. It will just cause the engine oil pump to pump harder than it needs to which is a mechanical loss meaning you are making your engine run slightly harder than it needs to resulting in a minor loss in mpg.
That is why most manufacturers have spec'ed this oil it flows better.
Even my BMW E93 twin turbo engine spec'ed 5-30W which certainly runs hotter off the turbo discharge than the Subaru normally aspirated engines do.
What oil does the Forester turbo run, anybody know? I am guessing a little thicker than the 20 weight...
That is why most manufacturers have spec'ed this oil it flows better.
Even my BMW E93 twin turbo engine spec'ed 5-30W which certainly runs hotter off the turbo discharge than the Subaru normally aspirated engines do.
What oil does the Forester turbo run, anybody know? I am guessing a little thicker than the 20 weight...
