1. (For old vehicles) Make sure your Fuel Cap is OK. In the US every year 147 Million Gallons of Fuel are lost due to evaporation.
2. When you park your car in the shade, you also reduce the amount of fuel that evaporates.
3. Don't top off, especially in the summer. The Gas is stored underground where it is cool. When you top off, some gas will spill out of your tank as it warms up.
4. Wider tires look good, but they are very bad for fuel efficiency.
5. Spoiler: It increases your wind resistance. It also pushes your car downwards, so you can keep better control at high speeds, but that’s usually not necessary.
6. A sunroof is great, but the optional wind deflector will increase drag.
7. Roof racks, Hood bug deflectors increase drag, Door wind deflectors increase drag.
8. Driving habits have a big impact on fuel economy, thus better drive improves fuel economy by 37%.
9. The filling trigger has three stages: low, middle, and high. You should be pumping on low mode, thereby minimizing the vapors that are created while you are pumping. All hoses at the pump have a vapor return. If you are pumping on the fast rate, some of the liquid that goes to your tank becomes vapor. Those vapors are being sucked up and back into the underground storage tank so you're getting less worth for your money.
10. DO NOT WAIT UNTIL EMPTY TO FILL UP YOUR TANK. Gas has weight and the more in your tank the more it weighs, however when less gas is present in your tank it reaches higher temperatures faster and thus evaporates more quickly. Ideally keep a decent amount in your tank but don't run on fumes.
And if you will get gas in the morning, you actually get more gas because the gas is cooler and denser.
