I'm about to put some 0W40 shell rotella T into my ATV with a wet clutch. It's full synthetic and although its not rated for motorcycles people have been ok with using it. It would probably help mileage all the time. It would also flow better than 10W40 at lower temps but near freezing 10W40 is fine too.
If my clutch slips then I'll try to remember to post it here.
Ian
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