So, in the above list from fluff34567, temperatures aside, when would I want 10W-30, and when would I want 15W-40? What does the factory recommend?
When I was still in the US, the factory would always recommend one oil grade for a particular engine, unless your usage conditions falls outside what was considered normal usage for the majority of people. Seems getting that information out of the local dealers is next to
impossible. They'll just tell you what *they* recommend, which is usually whatever they happen to stock. They are evasive when pressed for the factory recommendation.
Thanks,
-Ben