Re: gas stations
My wife was buying gas at our local cheap gas station. She tried the regular nozzle, but it didn't seem to work. Station attendant said, sorry, we're out of regular. So she tried the mid-grade, didn't seem to work. Station attendant said, sorry, mid-grade is a 50/50 mix of regular and premium. We still have premium, so you could try that.
So she put in a few dollars worth of premium and went off to find a different station to fill her tank with the regular stuff because she saves money wherever she can.

So, at least at that cheap gas station, midgrade is a mix of regular and premium.

R.