[Formulajones]

Yes and the E10 is not consistent either.

Years ago when this stuff started becoming more prevalent you could buy test kits on the internet, maybe you still can. Anyway I was finding some stations at the time were as high as 17% so it was a mixed bag of fuel at that time, and I haven't seen any reason why that would change today. In fact with the push in some states to increase ethanol content to 15% or more I have to wonder how much over that amount it will fluctuate since I've already seen more than that with the 10% mix.

This is why I said I simply tune my cars on the rich side of things, similar to what Cliff posted. Better to be safe since you never know what you're getting tank to tank. Keep it fat and happy and then you don't have to worry about it. I've been running the ethanol fuel in the classics for the last 20 years or so consistently, and 2 of them are daily driven. Never an issue, even with the bigger HP stuff.