You should decide what grade of oil you are using, depending on how and when you drive and where you drive. The grade spec from the manufacturer is supposed to cover any possible scenario. When you live in Southern California it makes absolutely no sense to use 0-40, if a 15-40, for example, is available. For my bikes, that here in NE Ohio only get use from May through mid-November I don't use anything but 20-50. I don't even buy a 5-.. even if it is on sale.