Thanks for the input all. There's a pretty good related discussion going on over here: http://www.peachparts.com/shopforum/showthread.php?t=90790

I ask because I changed the oil in the m104 last week using M1 0w-40. That's what MB recommends for M112/M113 and newer engines, so I chose it. (I exclusively use M1 products - different discussion, different reasons.) This week it occurred to me to question whether it was actually an appropriate choice. Looks like the answer is yeah, it's fine. M1 15w-50 would be fine year 'round in Dallas, as would M1 5w-40 (which is really repackaged Delvac 1 - best choice for a diesel, but sadly I am diesel-less these days.)

- JimY