[Old Professer]

Which would allow a less than scrupulous station owner to just bag the regular and high test nozzles on all pumps and sell only midgrade (actually regular)?

[thackney]

Which would allow a less than scrupulous station owner to just bag the regular and high test nozzles on all pumps and sell only midgrade (actually regular)?

Only if he got the trucker to deliver regular to the midgrade tank. Mixing is done at the truck loading facility, not at the local retail station.

The local station has at least three color coded points to fill the station tanks. The local facility will have no means of moving product from one tank to another without bringing in separate pumps to feed through the filling nozzles.

[Mike Fieschko]

Which would allow a less than scrupulous station owner to just bag the regular and high test nozzles on all pumps and sell only midgrade (actually regular)?

If a station tried that, they'd be caught very quickly. Enough people, including fire and police officers, know what tanks stations have and how the station's pumps work. Weights and measures agents would be at the station soon after your scenario started.