[danhr]

can't use pump e85 to bring octane up. The biggest reason why is because the octane rating is, because you won't know the ethanol content.

To use a higher octane fuel as an octane fuel is simple math right? if you have 1 gallon of 93 octane, and 1 gallon of 100 octane, if you mix the two together, you will have 96.5 octane. simple enough right?

well with e85, the octane and ethanol content vary so much. That's why you need a flex fuel sensor. So what you might get at the pump one day might be 97 octane e85, and the next week, it could be 104 octane. So it makes calculating how much you need to add, to boost your octane rating, rather difficult.... unless you plan on measuring the ethanol content every single time you fill up


You could use racing e85, but that would just be a wash, because that costs just as much as race fuel.