Originally Posted By: momo
5w30 or 15w40?
Either would be acceptable, but as you're in Canada, I'd probably go with the 5w-40* for better cold cranking. (*I assume you mean 5w-40, Not aware of a 5w-30 Rotella oil- their 10w-30 would be fine though)
with a 40 wt. you probably will lose .01% fuel efficiency but your engine will stay fresh as it ages. I'd have no problem running 15/40 in the warmer months, even better.