I've heard of folks using wvo, motor oil, and 2 stroke oil in a 50/50 mix with diesel. Won't work under air temp of 50f. I guess it gels or something.

I've been running both 2 stroke oil[left over from a long sold boat] and old motor oil [not used oil] in mine. Probably about a gallon of each.

Used motor oil I've heard ok if filtered to 5 microns or less. Never tried it myself...

Cheers,

Bill