M1 for all of my sh!t. Been using it for years. Is cheap enough and as far as I know $ for $ you won't find better. Never had oil related problems in anything. Is one of those things where an ounce of prevention....take care of your stuff and it will take care of you.

Great thread/poll Racerngr!

I found this site on a Cummins diesel forum. Haven't tried their oil yet though.

http://www.le-inc.com/productPages.jsp?productID=24

M-1 V-Twin in the boat and bike. Conventional in the cars and trucks.