How long do you have after the low-fuel light comes on?

Yesterday at 02:00 AM

If you are a particularly anxious person, seeing the fuel light appear on your dash can cause panic. But have you ever pushed it to see how much more range you can get out of your tank?

RELATED: How far can you reverse your car, legally?

The truth is that your car is giving you quite a lengthy warning before you need to call roadside assistance or get your friend to turn up with a jerry can.

So, how long do you have after the low-fuel light comes on in your car before you are stuck on the side of the road? Chances are, you probably have longer than you think, but beware – running your car on empty can cause serious issues.

How long do you have after the low-fuel light comes on?

Mark Harman, PR Manager for Isuzu Australia, says the answer heavily depends on your vehicle, your driving style, and what sort of fuel you use.

“Regarding the maximum driving range once the fuel light has come on, we cannot specify a distance to empty, since range is dependent on the driving style, speed, conditions and if the vehicle is loaded up or towing,” he told Drive.

Despite it being different for every vehicle, on average, at highway speeds, you can safely assume you have a range of between 50km and 80km. However, taking off from traffic lights and stopping and starting in traffic will cause your remaining range to rapidly decrease.

Australian comedians Hamish and Andy conducted a real-world test with their Audi SQ5 in 2017. The pair drove down a Melbourne freeway with the fuel light on and managed an impressive 111.9km before the car finally stopped.

How accurate is a low-fuel light?

Keep in mind that the low-fuel light may not be the best indicator of your range because of the way the sensor in your tank calculates how much fuel you have left.

Your car produces an indicator of how much fuel it has left in the tank using what is called a fuel sender. The sender is a buoyant sensor that tells your dash how much fuel is left in the tank depending on where the float is. When the float reaches the bottom of the sensor, it means your tank is in reserve, and the light will show.

Some people might tell you that when your low-fuel light comes on, your tank is going into ‘reserve’. However, vehicles almost never have a reserve tank unless it has been fitted as an aftermarket part. Instead, they enter what is called a reserve section.

The reserve section will, on average, be around 10 to 15 per cent of the tank's total capacity. But as your fuel gets lower, your sender will be more sensitive to events where your fuel may slosh to one side of the tank, like going around corners or driving on a sloped road, potentially showing that you have less fuel than you really do.

Car manufacturers have attempted to prevent the fuel indicator from showing an incorrect fuel level by adding baffles to the tank, but it’s still not a good idea to test the boundaries.

Low fuel will cause fuel starvation, which will make your engine splutter or stall. If you have a diesel vehicle, this could actually cause air bubbles in your fuel lines or increase wear on your fuel pump.

Running on low fuel consistently will also pick up the sediment in the bottom of your tank, causing your fuel filter and fuel pump to clog up with little particles, possibly further starving your engine of fuel.

What happens if you run out of fuel?

In the case of a petrol-powered engine, you'll get off relatively unscathed should you drive until empty.

However, if your car runs on diesel, your life will get a lot harder.

“As diesel fuel doubles up as a lubricant within the fuel system, it is advisable to maintain adequate fuel levels at all times and to avoid pushing the limit too far and running the system dry,” says Mark Harman

Basically, a diesel fuel pump has tighter tolerances and allowing it to run dry is a surefire way to ensure it gets damaged. Not only will your fuel pump be damaged, but your fuel lines, which must remain pressurised on a diesel car, will have air in them. You will need to manually prime all of the fuel lines to regain pressure in the system.

Running out of fuel in a car that uses petrol as a one-off is likely fine. You'll need to crank the car a little longer to allow the fuel lines to become pressurised again. Consistently running out of fuel in a petrol car will cause your fuel pump to run dry and cause excessive wear.

The post How long do you have after the low-fuel light comes on? appeared first on Drive.