Back to the original topic. At last weekend's speed/race contest at Whittier Narrows the speed flyers brought the standard fuel, as usual. They had two bottles, one from last year, and one brand new for this event. They test ran an engine on the stand and got a 1600 rpm difference between the old stuff and the new stuff. Interesting results. I think the old fuel was good for nothing by week killer!
The fuel was in plastic bottles. IMO the reason for the difference permeation, by water, through the plastic diluting the alcohol.
Any other ideas?