Where are you finding e90? You mean e10? As in 10% ethanol? I don't like that stuff in the least, and the e15 is even worse. E85 is 85% ethanol and 15% 93 pump gas. E85 was designed as a safe alcohol or methanol substitute. It has enough gasoline in it to not burn clear in the daylight. The vapors are less volatile as well. I've seen an alcohol dragster backfire, and it took the crew 30 seconds to figure out they were on fire. 6 people went to the er with severe burns. E85 was a safer alternative to that. But when they started with the ethanol blends, it was brought to the pump as another option. If you are going to reconfigure your weekend hotrod to run on e10, why not step it up and run e85 with more power, and you can tell the hippies to f-off since your old hotrod runs cleaner than their Prius. Once again, although e85 is available at some pumps, they are not yet mandating, or even trying to mandate it as a primary fuel. Maybe someday when/if manufacturers start offering decent e85 vehicles, but that isn't happening yet. E15 got shut down, it will be a while before e85 gets anywhere close.