#1: Fill up at half tank for fuel efficiency
This is related to a lot of factors, including gasoline’s tendency to evaporate at temperatures not much higher than room temperature, which reduces the pressure on the fuel line.
If you’d like to test this, next time you fill your tank all the way up, reset your trip-odometer. Drive the car until half tank, and fill it back up again, recording how much you put into your tank and your trip-odometer reading. Divide the miles driven (your trip-odometer) by the amount you put in your tank to get your MPG. Then, reset your trip-odometer and drive until your vehicle’s “Low Gas” light comes on, and repeat the earlier steps of computing your MPG. Half tank will consistently give you better numbers.
#2: Fill up when it’s cold outside
This won’t prove as dramatic as #1, but it helps a little bit. Gasoline expands when it heats up, providing less available energy per unit of volume. Gasoline filling stations in the US are not required to compensate for temperature variations when selling product to end consumers. However, Canada does. So another recommendation would be to move to Canada.
#3 Don’t worry about preferring one brand of gasoline over another
Different brands of gasoline don’t make as much of a difference as the Gas company’s marketing wings would make you want to believe. The additives are the only thing that make much of a difference, and just how most people can’t tell the difference between Pepsi and Coke, your car won’t notice much of a difference. The US Government mandates minimum requirements for gasoline additives, and you’d be surprised that a lot of what you find at the pump has nothing but a generic additive (even for branded gasoline locations). For example, up until about 2-3 years ago, pretty much all gasoline sold in the Central Florida area had nothing but the generic additive in it. Except that ExxonMobil is special. Their gasoline had 2x the generic additive as everyone else (it’s amazing how true this stuff actually is…).