There are lots of ways to save money on gas

One of the best ways is to always fill up in the morning.  Gas expands as it is heated and literally, if you fill up in the afternoon after the gas has heated up in the underground tanks at the gas station during the day, you will get less gas for the same amount of money.

When gas prices are rising, you should get gas as frequently as possible.  This is, in effect, dollar cost averaging your gas purchases, which will make your overall cost lower than if you wait until your tank is empty to fill up.