I'm 100% with you on there not being a "magic number" for everyone. I was looking for a general range that e10 seems to perform best at.

Your comments on how much ethanol the pumps labeled as 10% really contain reminded me that I was looking for some type of ethanol tester to check the local stations. I know Quick Fuel markets one targeted towards the e85 crowd, but I'd like to be able to run spot checks on the e10 stuff to see what it really shows and how consistent it is from fill-up to fill-up...