clemsonfor
Super Member
I notice my YM336D service manual recommends 30wt (and only 30wt) for anything above 50F. It doesn't even mention 15w-40.
Is 15w-40 new? Is it a safe replacement for straight 30wt?
Yes you can run even 5w-40 in a syn and be fine. That oil was not around in 1980! I would never run straight 30Wt at 55F. That stuff is like Honey and will take forever to flow at that temp. 15w-40 will flow like 15W cold and 40W hot.