The key is the % you run on different injection systems. Some engines will run on pure vegatable oil too.. The closer to 100% you get the more residue is left. Bio has viscosity variations with temperature. Its a work in progress. No one says it wont work, just be carefull how you use what %blend. HEUI's are very succeptible to the thickening engine oil from deposits left after the combustion process. It appears everyone agrees 5% is ok.