Why You Should Always Keep a 1/4 Tank of Gas in Your Car

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Everyone knows that keeping gas in your vehicle's fuel tank is a must. But you may wonder what the minimum amount of gas is that you should always have in your fuel tank. Some experts claim that you should never let the fuel level drop below 1/4 of a tank. In the past, this recommendation was due to sediment forming at the bottom of a gas tank. But, more recently, it is believed that gasoline or diesel fuel helps keep the fuel pump found in modern gas tanks cool, making going below 1/4 tank of gas less troublesome.

However, the fuel pump is a vital part of your vehicle's fuel system, as it makes sure your engine gets the fuel it needs to keep running. So, here's why you should avoid letting the fuel level get too low in your car.

The effects of letting your fuel get too low

The fuel tank of your vehicle holds either gasoline or diesel and feeds it to the engine via the fuel lines. It is a vital part of the vehicle's larger fuel system. In older vehicles, manufactured before the 1990s, fuel tanks were made primarily of metal and tended to rust over time. This could cause a problem if the fuel pump sucked up any sediment within the fuel tank and sent it to the engine. In addition to potentially causing problems with the fuel pump, this rusty sediment could also plug fuel lines, as well as the fuel filter, and could damage the engine itself.

Luckily, newer fuel tanks are made of high-density plastic, negating the formation of rust. That doesn't mean that sediment can't still get in your fuel tank. It can, usually from bad fuel. But the chances of this happening are very unlikely.

Another concern with letting your fuel level fall below a 1/4 tank is that it could cause problems with the fuel pump. In modern vehicles, the fuel pump is located within the engine where the fuel helps keep it cool. When the fuel level falls below the fuel pump, the pump starts taking in air, which then generates more heat. This overheating can cause the fuel pump to wear out faster than normal or even cause it to fail completely if it gets too hot. In the past, this wasn't a problem because the fuel pump was located outside of the gas tank and didn't rely on the fuel to help keep it cool. Plus, it didn't cost as much to replace since it was easier to get to.

If you do drive often with a low fuel tank, you could encounter part failure, including problems with the fuel pump and fuel filter. Here are a few symptoms to look out for that indicate potential problems with your fuel system.

Fuel pump

The fuel pump in a vehicle pumps fuel from the fuel tank to the engine. In addition to performing this function, it also makes sure that the fuel stays pressurized while on its way to the engine. The fuel pump is located in the fuel tank on modern cars, and problems can occur when the fuel pump either becomes clogged from sediment in the fuel tank or stops working due to wear, usually from working too hard or after long intervals of time. A fuel pump should last you at least 100,000 miles or longer.

Signs of a bad fuel pump. If you are lucky, you should never have to replace the [fuel pump, as some cars can go many miles without this essential piece of hardware malfunctioning.

Occasionally, though, a fuel pump can wear out, requiring you to replace it. Some signs that your fuel pump needs replacing include:

  • A vehicle that is hard to start. This is caused by fuel not reaching the engine.

  • Hesitation while driving on the road. In this case, fuel is reaching the engine, but the flow is being impeded somehow. A failing fuel pump can cause this problem.

  • Decreasing fuel mileage. This is a problem usually caused by a failing release valve, which is located in the fuel pump.

  • Overheating can also signify a problem with the fuel pump. This is caused by the engine having to work harder than normal to pull in the fuel it needs to run. If the engine gets too hot, the vehicle could stall or the engine could fail altogether.

Fuel filter

The fuel filter is a component that filters the fuel before it gets to the engine. While a fuel pump has its own filter, sometimes it does not catch all of the particles. The fuel filter, located between the engine and the fuel pump, is another stopgap measure to help catch any of these remaining particles that make it through. Sometimes, though, the fuel filter becomes clogged and needs replacing. For the most part, a fuel filter should last you around 30,000 miles or two years of driving.

Signs of a bad fuel filter. Just like the fuel pump, a fuel filter can go bad if it becomes clogged with sediment from the fuel in the gas tank.

Unlike the fuel pump, the fuel filter is located outside of the gas tank, making it easier to get to and replace. Some signs that the fuel filter is going out or has failed include:

  • The engine shakes when you are sitting idle in your vehicle.

  • Your vehicle fails to start due to the fuel flow from the fuel tank not reaching the engine.

  • Difficulty in starting your vehicle due to a partially blocked fuel filter.

  • Your vehicle struggles while you are driving on the road.

  • Your vehicle stalls while driving.

Keeping your fuel tank at least at the 1/4 full mark can help protect both your fuel pump and fuel filter. If you run into problems with either the fuel pump or the fuel filter, have one of our expert mechanics replace them for you.


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