MTBE/ETBE is banned in many places due to groundwater contamination. But ethanol-less gasoline wouldn't be a disaster either, it would mean the refiners would h

MTBE/ETBE is banned in many places due to groundwater contamination. But ethanol-less gasoline wouldn't be a disaster either, it would mean the refiners would have to do more processing (alkylation, reformation etc.) to increase the octane of the gasoline, which would increase costs. But OTOH without an ethanol mandate there might be less cost via agricultural subsidies etc., so it wouldn't surprise me if the total cost to society would be less. There are also some other octane boosters that could be used (which aren't environmental disasters like lead, or arguably corn ethanol), like aromatic amines.