Can gas last longer or less depending on what gas station you use?

Question

I can drive the same way, the same mileage but it seems my gas last less when I fill up at the discount stations. Do discount gas stations add something so they can sell the gas cheaper?

Answer 1

The only thing that can be happening is that the gas station has not upgraded the gasoline boiling temp grades.

There are four types of gasoline, summer, spring, fall and winter and if you have a spring gas and the temp is very hot then yes the gas will evaporate quicker causing less mileage.

Answer 2

They all get their gas from the same sources.

Why would they add something, that would only raise the cost to them? In other words, anything they could add (except for water) would cost more than the gas would.