I have been adding straight, new soybean oil to my tank for a few weeks now. It has not been cheap (~$20 for 5 gallons from Smart & Final), but I did it as an experiment just for fun. I'll eventually scrounge my own used veggie oil, filter it and use that.

Anyway, I've encountered no problems whatsoever. I first premixed the veggie oil in a 5-gal. gas can with regular diesel, then dumped the mix into the tank. The two mix up beautifully and don't separate, especially in my climate where temps are usually hot (your results may vary). At most I was running about 20 percent veggie oil.

I noticed a slightly smoother idle with the veggie oil, and a more aromatic exhaust. I also noticed that debris seemed to build up in my fuel prefilter a bit quicker than I would expect with regular dino diesel.

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'81 300TD turbo <<sold 12/05 to another diesel nut