Just started running 91 octane ethonal free in my sho (2) tank fulls now. Any thing wrong with this ? Good bad or ugly things gonna happen ? When I picked the car up it had a full tank not sure what was in there got good mpg like 22.5 my normal drive routine. First time I filled up went with 93 octane 10% ethonal , mpg was 19.5 -20. Performance was good both ways. Still new to the car not sure what to expect. Man I put that e- free fuel in and holyshit its like a whole new machine. I know about the fuels and things was just wondering how all yous feel about it. Oh yeh the car is stock. I like the e free gas but if it’s gonna hurt gotta say bye bye.