I am perplexed. What is the error?
Ethanol increases your octane rating. When you lose the ethanol, you are left with the low grade non-ethanol-gasoline octane rating(in theory). Nowdays almost all gasoline has some ethanol in it. I don’t pay attention to octane ratings anymore, but before they started adding ethanol to everything, the middle octane rated fuel at the pump was ethanol. The lowest octane rated fuel was non-ethanol, the highest octane rating was premium. The difference between premium and the lowest octane rated fuel was that after filling the underground tanks, the tanker driver(or the station manager/owner) would dump an additive down into the tank of the premium grade fuel. Without doing that, the two non ethanol fuels were identical. At some point(about 5-8 years ago I think) many stations started putting ethanol in ALL grades of fuel even without advertising it at the pump. You still had 3 grades of fuel, but only one of them CLAIMED to be E10. The truth is they all had ethanol in them.