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October 20, 2016

Is It Bad For Your Car If You Drive Until You Run Out Of Fuel?

Empty_gas_tank-iStock_76575303So I did this the other day.

Well, I didn't actually run out of gas, but after sitting in rush-hour traffic for two hours, my "Miles to Empty" indicator dropped in one step from 14 miles left on the tank to alternating between zero and one mile left.

I pulled off the freeway immediately to find a gas station and along the way, watched it creep back up to three miles to empty and breathed a sigh of relief.

Empty_gas_tank-161019-1820I shared a photo about my close call on my Facebook timeline, and it didn't take long for the mechanics in my social media world to scold me for allowing it to happen. In my defense, I was on the way to the airport the other day and saw that my indicator said I had 77 miles left on my tank. The trip to and from the airport is about 50 miles, so I figured I'd just get gas when I got home; it seemed I had plenty of gas to make the trip but I didn't have time to fill my tank and get to my flight on time. And I certainly wasn't expecting the 25-mile return trip to take two hours in bumper-to-bumper traffic.

Oh, and in my defense, I've driven my Ford Fiesta more than 63,000 miles, and I think it's only gotten down to fumes about three times. 

So, what's the answer: Is it bad for your car if you drive until you run out of fuel?

On the simplest level, feeding your engine from the bottom of the gas tank is very similar to drinking the last cup of coffee in the pot: those coffee grinds and sediment that have settled to the bottom of the pot? Similar stuff has settled to the bottom of your gas tank, and if you send that into the fuel system, you risk clogging filters and lines along the way to the engine.

Empty_gas_tank-iStock_1401101Sure, sure, the fuel filter is always sucking from the bottom of the tank, right? Yes, but when the tank is full, any particulate present in the tank is more likely to be swished around and up into the greater volume of liquid. As the volume of gas decreases, the percentage of particulate increases and is more easily sucked into the fuel system. That sediment can plug up the fuel filter and taxes the fuel pump. Fuel pumps are very expensive!

I've also been told that allowing the gas tank to stay below 3/4 empty for long periods of time can also contribute to moisture condensation within the tank, which could also negatively affect the quality of the fuel. During winter months in cold climates, moisture in your fuel lines can freeze and prevent your car from starting.

So, whether or not it's an old wives tale, most people believe it's a good idea to try to keep your tank above half full in freezing climates and above a quarter full the rest of the time. What say you?


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