I have done lots of research on different used oils being run as fuel. My choice is WMO or WATF. I'm having procurement issues right now but I have run it in the 300SD in the past.

I cut my oil with about 15% RUG, let it settle, and filter it through a 1 micron bag filter. I only have 5 gallon buckets, so it can be a laborious process but I like saving $20 per bucket I pour in. I usually have some D2 in the tank or in the mix as well. The highest concentration I have run is about 50/50. That would be 5 gallons on top of an almost empty tank of D2.

__________________
1991 F250 super-cab 7.3 IDI. (rebuilt by me) Banks Sidewinder turbo, hydroboost brakes, new IP and injectors.
2003 S430 - 107K
1983 300SD - Tanoshii - mostly restored ~400K+.
1983 300SD - Good interior. Engine finally tamed ~250K.
Monark Nozzle Install Video - http://tinyurl.com/ptd2tge