Rowboy,
If you saw this firsthand why didn't you do yourself and all of us a favor and report it to the Dep.t of Consumer Affairs or whatever the appropriate state agency would be?
They could test the fuel in his tank and bust him with a hefty fine for consumer fraud amongst other things.
If they knew anyone seeing this would report it then things like this wouldn't happen as often, and we'd get the gas we paid for.
I've often had a car not ping on one tank of premium and ping on the next tank from the same station/pump a week later.
The next tank would be back to normal. All this with the same engine settings and similar weather conditions. The fuel had to be different.
Later,