Well late reply, but I just joined....I have successfully for YEARS ran 100% WMO in my 6.2 trucks. I live in Ohio, and I was running it 100% in the winter even. It would surge badly for a minute or so during the winter cold starts (0-30*f) and die if you tried to take off without ample warmup time. I never plugged in it regularly, but when I did, it helped alot, as you could imagine. The truck ran quieter and had more power. I know "in my mind" that oil burns ALOT hotter than diesel. I have witnessed it in my own waste oil heater in the shop. The more waste oil I burn compared to diesel fuel, the more I have to add air. I cut the wmo back some and achieve the same heat output as fuel.
ANYWAYS,
I have also ran it in my 6.5 with mixed results. It's a 94 with an older BD Diesel 40hp chip, holset he351cw with a 67/76 mm upgraded exhaust, holley blue lift pump, and top mounted intercooler. I have also bumped the timing up to 2.00btdc. With just 50/50 mix, it would randomly surge and buck, and some intermittant excessive ratteling. "I" am ok with that, but I'm sure most people wouldn't like it. I did try 100% and it ran, but shortly went into a reduced power and I had to pull the optic sensor for a cleaning. That is not a job for everyone. I have a few scan tools as well as a TEC2, so not too big of a deal for me, other than the work to do it. But I would not recommend it.
6.2's yes, all day long.
6.5's not so much as long as they are electronic. That stupid optic sensor.