Been running E-10 for well over 20 years here in northern Indiana..Not much choice in the matter, as it's all that available except for one station about 20 miles east of me, and way too far out of the way to go for fuel...And in all that time I have yet to have ONE SINGLE issue with any of my cars, motorcycles, lawn mowers, snow blower, chain saw, etc...No gunked up carb, engine problems, or anything due to the fuel...I had a varnish issue with a '67 VW Beetle I bought (had been sitting for about 4-5 years), but I had to rebuild the carb due to Seafoam loosening up crap in the fuel system and it made it's way into the bottom of the float bowl...Nastiest orange crap I'd ever seen in a carb...Was surprised the car ran at all, as the main jet was completely plugged...100% gasoline will turn to varnish over time just the same as E-10 will...The only negative thing attributed to ethanol is that it attracts moisture, and that can lead to rust in the gas tank...During riding season the bike doesn't sit still long enough for the fuel to go bad, and in the winter I treat it with Seafoam...