There are a substantial number of existing aircraft that are safe to operate on a subset of automotive gasoline (93 octane, ethanol-free). The FAA says to do so

There are a substantial number of existing aircraft that are safe to operate on a subset of automotive gasoline (93 octane, ethanol-free). The FAA says to do so legally requires the purchase of a supplemental type certificate for thousands of dollars. There's no inspection or modification of the aircraft. It's just a piece of paper. The FAA could fix the problem for those aircraft with the stroke of a pen.