scottmn1

For the life of me I cannot understand why anybody would take the old, nasty, black, used motor oil that you would not want in your engine anymore, then turn around and put it right back in your fuel system. If it was good for your engine, why not just leave it in there in the first place? I just don't get this reasoning

xtoyz17

Because it burns and if filtered properly won't do any damage. Cummins even states SOME used motor oil is acceptable. I don't remember the number off hand, but I believe it was 5-10 percent.

Muddin_dude06

I have used outboard motor 2-stroke oil a lot and just recently used my used motor oil. I always add 1/2 gallon to my tank of whichever I have...