Oil viscosity - more difference than I would have thought

[GasSavers_BEEF]

but horsepower can vary greatly from engine to engine due to a lot of factors, a big one being RPMs.

your car probably redlines around 6-7k where as your motorcycle probably goes well over 10k.

a better determining factor would be torque ratings.

I'm not trying to discredit what you say as it may be true but motorcycles in general run really high revs giving them the HP that they have and the flip side being that they have very little torque (relatively speaking)