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Road Myths: How long can you drive after the fuel light comes on?

Posted Oct 25th 2010 10:16AM

Shaun de Jager, Founder of speaks out about road safety and road related issues.

How far can you go once your low fuel light comes on? This is a question that drivers have been pondering since the first car rolled off the production line. It's also a question that most dread to learn the answer to.

The simple answer is that there is no simple answer. Every vehicle is different and so is every driver. If you are a more aggressive driver or prone to driving fast, you will burn more fuel per kilometre than a more relaxed driver does. That's assuming you are comparing drivers with the exact same vehicle because every vehicle is different, too. Additionally, stop and go traffic will certainly burn more fuel per kilometre than maintaining a constant speed.

Okay, I guess that leaves us with averages, guesses and personal opinions. Some mechanics will say you can get anywhere from 50km-100km once your "low fuel" light switches on. Well that's still a rather large range but each mechanic you ask will also say "it depends on your car and how you drive it." Hmm, still not very helpful, I know, but it's true.

It also depends on the size of your fuel tank. Most tanks are set to trip the low fuel indicator as the level drops below 20% to 25%. Keep in mind, though, that the tank on a Chevy Suburban is a lot bigger than the tank on a Honda Civic. I used to drive a 1986 GMC pickup truck and got about 80 km before I ran it dry and that had a 110-litre tank. My 1996 BMW also got about 80 km before I was on fumes and that only had a 55-litre tank.

Most cars today are so advanced electronically that they constantly adjust fuel and air delivery to provide the perfect fuel/air ratio. Older cars, those that are carbureted, don't do that and changes in air temperature and even altitude can have an impact on how much fuel you use per kilometre. If your car runs too "rich" (more fuel than is required) you are wasting fuel. Changing the mixture will make a difference. In newer cars that is done on the fly, whereas a carbureted engine will have to be adjusted manually.

Do you fill up as soon as the 'low fuel' light appears?
Yes, always741 (55.5%)
Sometimes332 (24.9%)
No263 (19.7%)

Everyone will say something different about how far you can go once your low fuel light comes on so really there is no "good" answer. Even if you carry a small can of gas with you and run your tank dry a few times your results will vary because the conditions of how you burn fuel will vary with each tank. Aggressive driving, higher speeds, stop and go traffic are all variables that burn more fuel. I would caution you though to NOT try running your tank empty just to find out yourself. Running out of fuel can also damage your vehicle in a couple of ways.

Firstly is the fuel pump. The main action for which it was designed, pumping fuel, also keeps it cool. If there is nothing to pump, the pump itself will overheat and eventually burnout or at the very least cause some degree of damage. It may not fail the first time you run out of gas or even the second time but you are in fact causing some level of damage to the pump. Eventually it will cost you.

The other concern is the "crud" that is found in all gas tanks. Cars have a fuel filter to try and prevent this crud from reaching the engine but they can only do so much. Smaller particles still get through and end up in your engine which can eventually lead to engine damage. As your fuel levels get very low, the fuel pump is more likely to pick up this crud. At the very least your fuel filter will become clogged resulting in it not only needing replacing but it can also lead to restricted fuel delivery to your engine.

Basically, you could "run out of gas" because fuel can no longer make it past the filter leaving you stranded on the side of the road.

Vehicle maintenance is also an issue. Ensuring you perform your tune-ups and oil changes at regular intervals and maintaining proper tire pressures also will improve your fuel economy.

As I said earlier, this really comes down to averages for each driver and each car. With that in mind, a fellow in the U.S. decided to get some averages, from average drivers, for the cars they drive. He started a website called "Tank on Empty" that encourages drivers to submit their own results of how far they could go, in their specific vehicle, before they ran out of gas.

Keep in mind that the results are in miles and not kilometres, but you can convert them buy multiplying each mile by 1.62 to find out roughly how many kilometres each driver squeezed out. The results are wide and vast but it's the average you should pay attention to for your specific vehicle. Still, it's only a guideline.

In closing, the rule of thumb remains: If your fuel light comes on, find a gas station as soon as you can.


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Girl Wed

This was useless

March 11 2014 at 8:24 PM Report abuse rate up rate down Reply