Can you fill a cars fuel tank with more or less gas on cold day?

You can fill a car's fuel tank with more gas on a cold day. This is because the gas is denser when it is cold and therefore occupies less volume. For example, when gasoline is cooled from 25°C to -10°C, its density increases from 0.73 g/mL to 0.77 g/mL. This means that the same volume of gasoline would weigh more on a cold day than on a warm day and would therefore contain more energy. So, if you fill your car's fuel tank on a cold day, you are actually able to put more gas into the tank and therefore get more mileage out of your gas tank.