You can improve your fuel efficiency by making adjustments to your car and driving. This two-prong approach will get you the most out of your gas.
Only use the fuel type the manufacturer recommends. Secure the fuel cap completely when you fuel up. Inflate the tires to the right amount.
These things will get your car to operate as the manufacturer intended. Then look at the amount of weight you are carrying around.
Remove excess weight as this will put more strain on your engine. Replace your air filter as needed. This too will strain your engine.
Adjust Your Driving
First and most importantly, go easy on the gas. Those with a heavy foot consume a lot of gas.
While driving, avoid idling for long. This is using gas and you aren't going anywhere.
Drive in the highest gear you can without putting extra stress on the engine. The highest gear possible for your speed reduces the strain on the engine.
Plan Your Trip
First plan your trip and all the stops you need to make. This reduces the amount of commuting you do.
Plan to fill your tank up first thing in the morning. Temperatures are cooler then and that makes gas denser.
As the fuel flows through the pump you are getting up to 2.5% more gas by volume. This doesn't sound like a lot but could save you $10 a month.
Plan to fill up at locations with the lowest price. Online resources like the gas buddy map let you look up the gas prices near you.