Since gasoline is more dense in the winter, I should be getter more mass per unit of volume. It makes sense that I would be getting more gas for the same price when its colder.
How much different is the density of gasoline at 20C vs. - 10C? Is there a significant difference?
How about day/night temperatures? Should I be buying gasoline at night when it is at its densest?
Remember that gas stations keep the gas in a tank underground. The temperature underground where the gas is doesn’t change change enough to make a significant difference in the volume of gas.
Snopes goes into some detail about this.
The American Petroleum Institute uses 60F as standard for density correction. Many states oversee the validity of metering at the pump via bureaus of weights and measures-there’s usually a dated sticker on the pump.
This works both ways, product can be returned to the wholesaler/refiner etc.
No free lunch, though the “oil companies” usually pay for the water in the tank, too.