This Is How Much Gas You Should Be Keeping in Your Tank

Keeping this much gas in the tank can help prevent damage and extend the life of your car.

pump gas carPhoto: Peter Gudella/Shutterstock

How much gas should be in your tank?

Nothing is more annoying when you’re cruising on a road trip or commuting to work and realize something urgent: you need gas. Between the time it takes to fill up, the cost of the gas, and just the general inconvenience, you might be wondering whether you can just cruise a little bit longer without stopping. Maybe not so much, according to experts who say there’s actually an ideal amount of gas to keep in your tank. (Don’t miss the reasons why your car won’t start.)

For starters, it’s important to understand how your gas tank works. In your gas tank is a fuel pump, says Bill Evans, who’s worked with cars for over 30 years and is now manager of J & E Auto Body in Clark, New Jersey. This pump runs from the gas tank to the motor, supplying fuel. As the pump runs, it heats up—but when it’s submerged in gas, the fuel acts as a coolant to stop the pump from overheating. If you’re running on less than a quarter tank of gas, the pump will overheat and end up failing sooner than it should. What’s more, driving around on empty can cause condensation in the walls of your gas tank, diluting your fuel, and causing rust, according to Richard Reina, a product training director at And unlike these simple car problems, engine rust and a broken fuel pump aren’t things you can fix yourself.

You may still feel driving on empty gives you more fuel for your buck. But, in addition to increasing the potential of longterm damage to your car, driving on empty actually hurts your gas mileage. “If you’re driving around on empty, the fuel pump is going to start picking up everything on the bottom of the tank,” Evans says. This includes sediment from dirty gas and tank condensation. Not only can this damage your fuel pump and motor, but it actually makes your gas mileage worse. “As long as you have a quarter tank of gas, your gas mileage is going to stay as optimal as it could,” Evans said. “The filter isn’t getting hot. The motor isn’t working as hard. That all helps on your gas mileage. If you’re keeping a quarter a tank of gas or more in the car, you’ll prolong the life of the fuel system parts.”

So there you have it—maybe it’s time to break your habit of using the last drops of the final lire of fuel to roll to the gas station. And while you’re at it, focus on breaking these other bad habits that are shortening the life of your car.

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Originally Published on Reader's Digest