[Phantom]

You do not solve an engineering problem with regulation. The simple solution to fix that issue is have the pump mix the fuel at the pump handle to get the mix you want. It would work like this have two hoses running to the handle actually to a connector just before the handle. The larger hose has its standard e10 the smaller hose has e85 the user asks for e15 have the pump do the calculations for how many GPM the pump for each hose needs to flow. That way the only extra amount of e15 that someone might get is the 1-3oz that would be in the mixing connector just before the handle.

Do they take the same conisderation for cars that have to use high octane? If a turbocharged motorcycle with a 3 gal tank needs 93 but the last person got 87 then the resulting octane could not be 93.