Why W number in oil dropping so low? By twowheeler (Read 816 times)

[twowheeler]

Many manufacturers are producing odd weights for newer cars. Some are 0W's. Also why do motorcycles and diesels normally require 15w-40 or 20w50 in the W portion? If the oil is 40-50 weight or any weight for that matter when at temperature why cant you run say 5w40 or some higher winter weight? Why have suck thick oil at startup if its all 40 or 50 anyway?

A lot of guys are using 5w40 rotalla in their bikes so why is a standard bike winter weight usually 15 or 20?

[randy]

It never did make any sense to me either. The oil you pour in cold from the can always seems thicker than the oil you drain from a warm engine. Alot of the manufactires are running closer clearances in their engines and want a lighter weight oil for start up. I think the reason behind motorcycles and the heavier weight is operating tempurtures and r.p.m.s