Originally Posted by RimasRS
I guess something like that. In location where I live there is a petrol which rated as 93 but it's a mix with 15 percent bio ethanol and it's a bit cheaper even than 91. So I think 93 octane reached by mixing 91+15% ethanol and now it is rated like 93 octane if you know what I mean.
My question is it better than clean 93 safer stronger?
P.S. I know that E85 (bio ethanol) is not good for rubber seals and things like that.
Depending on your location the way they rate octane is actually different. You likely wouldn't harm anything in your car by running a low mixture and may boost your detonation resistance a bit, but you can give it a try and log your car to make sure. Yes, E85's high ethanol content it is bad for seals over time, but if you are running a low mixture with pump gas it shouldn't be too bad. Over an extended time of continuously utilizing it you may notice it effect the car though.