You won't find M1 10W40...if that's the weight you like and you want a syn, I recommend Redline 10W40 for your engine, although if it were me, I'd go with their 10W30 if the engine is healthy and not using much oil. What weight does your owner's manual recommend?
The other question is do you want to go with synthetic or non-synthetic. You'll have to tell us how you drive and how often you want to change your oil. )