The only downside to running B20 or higher is it will clean out your fuel system as bio is a great solvent. So if your going to run it carry an extra couple of fuel filters because your going to clog the first couple up, but once your fuel tank is cleaned out it will be fine. I stated down side and it is because of having to change the filters but it's also a major up side in that now your injectors, lines, pump etc are all nice and clean and working much better.