Warranties of older vehicles would be voided by >10% ethanol in fuels.
There's a reason for this, and manufacturers did not want to get stuck with the tab fixing fuel systems that failed because of excessive ethanol.
The gambit here is to destroy older vehicles with crappy fuel, and it may be remembered by those who drove high compression engines back in the day with tetraethyl lead additives to prevent valves burning. Suddenly, you couldn't get good gas, and if you wanted it you blended your own with avgas (which had a far higher lead content and about 105 octane) or used some other additive to keep from destroying your engine.