He says his loader tractor (a 1530) runs better on it, and so does his pickup, but I haven't asked lately.
He has two old underground tanks from about 1970. Years back I found bits of gravel or rust in his fuel when I put it through a funnel with a screen. I told him, and he didn't believe me. Maybe it's gotten worse. Maybe that's my problem, but it doesn't explain the tractor running better after getting E-10. Your mixture idea does. I'll ask him if his truck has been missing or sputtering.