Think about this. If you buy 2 gallons of premium from a pump where multiple grades share one hose, you are getting 1 gallon of premium and 1 gallon of regular. Based on this, I think I would be better off buying 2 gallons of the non-alcohol 90 octane from a one-grade, one-hose pump. I do know of a station that has multigrade pump where each of the 3 grades has its own hose, so that is another alternative.

Somebody check my math:Assume the hose is .5" ID and 8' long. That's (.25^2*3.1416*96) cubic inches of volume = 18 cubic inches or 0.01 cubic feet or roughly .08 gallon. Does seem to match what Taildragger said.

You may get some mixed but i doubt that its a gallon. I drain the hose and its no where near a gallon.