We’ve all been there: late night on the freeway, unsure about the distance to the next fuel station, and your car’s fuel gauge is desperately close to “E.” How far over that red line will that needle go, anyway? A stranded car is more likely to be struck by another car or vandalized. It doesn’t make sense to risk your lower auto insurance costs unnecessarily. You may also wonder if there is any other danger besides the risk of being stuck on the side of the road.
Low Fuel and your Engine
The short answer is that it’s not mechanically dangerous or seriously damaging to run your car until it stalls from a lack of fuel, but it’s not the best practice to keep your car in good shape. As far as regular gas engines are concerned, little damage comes from running the tank dry (diesel engines are a different story). There is the potential for you to wear the components of your car more when running near empty, though.
First of all, the fuel pump uses fuel in the tank to keep it cool; if the tank is near empty, the pump’s ability to cool itself is greatly reduced and it will wear more quickly because of the increased operating temperature. Second, gas is seldom perfectly clean, and sediment tends to settle in the bottom of your tank; if you suck the tank dry, this sediment will get into your fuel system, potentially clogging fuel lines and filters.
So… How Close to Empty Can You Go?
This, unfortunately, is a difficult question to answer, and depends on your vehicle and driving habits. Gas gauges are a reasonably imprecise way of telling how much gas is left in a tank once it falls below 1/8 tank. Often, the needle seems to move much faster towards the bottom half due to irregular tank shapes. The best way to know how far you can go is to keep track of your distance using the “trip” feature of your odometer.
Start with a full tank of gas and set the “trip” meter to zero. Next time you fill your car, divide the number of miles you’ve gone by the amount of gas you put in to fill your tan. This gives you the average gas mileage (note that this can be very different depending on whether you are driving on the highway or in the city–it’s good to know both). You can look in your vehicle owner’s manual to see how much your tank will hold, which you can then multiply by the gas mileage to get how far you can go on a tank of gas. Use your city gas mileage to get a lower limit on the distance, and your highway mileage for an upper limit. Now you simply need to reset your “trip” odometer at each fill-up, and you will always know the worst-case scenario for how far you are from running out of gas.
Despite the fact that little damage is done to your engine, running out of gas on the side of the road is seldom a risk worth taking. Know how far your car can go, and don’t take and unnecessary chances. Finally, if possible, carry a small spare tank in the trunk in case you are stuck.