Diesel Rug blends have been done when using WMO to make it start easyer, I have ran 60% virgin motor oil Diesel blends with no problems is stock fuel system in 91 Idi, your 6.o should have plastic fuel lines, so should be ok to run BIO, ford says no more than 10%....throw that truck away and get a Idi, when diesel gets more expensive just burn suntan lotion.