My Dad's diesel still runs good on fish and chip cooking oil. Methanol ,KOH and used oil and away you go. Byproduct is soap, good enough to clean parts with, and easy on the hands, Madge
Down side is labour intensive and getting a ready supply of used oil at the right price. Feed mobs are buying the stuff up to process and send to Japan as stockfeed.
Keep a dream in me head to modify a Honda diesel to run in an ultralight and fly around on home brew. Just have to work out additives to keep the stuff from turning into jelly for sub zero temps. Already better pour point than regular pump stuff. Fridge test at -4C has pump stuff turning to wax and the home brew still liquid. Just the same, wouldn't want the stuff to go to goo at cruise.