I was running low on gas on the way to work this morning and had to pull in to a gas station I don't normally frequent... and noticed an E15 pump. I used to mix 93oct and e80 to get about e30 in my e92 335i, but didn't realize they had an e15 straight from the pump... Any gains to be made on e15? I do realize regular 93oct gas is up to 10% ethanol anyways but the cooling effect of higher ethanol goes a long way in Texas...

 

I would treat E15 the same as regular pump gas as far as tuning goes. Since as you mentioned regular pump unleaded has 10% ethanol usually, an extra 5% ethanol is not going to make a difference on anything one way or the other.