How much gas is left in the tank when the fuel light comes on?
The fuel warning light comes on based on the vehicle's system measuring the minimum amount of fuel remaining, thereby estimating the possible travel distance for the driver.
The fear of running out of gas in the middle of the road is something no driver wants to experience. But when the fuel light comes on, how far can you go before your car comes to a complete stop? The answer isn’t simple, but it’s not too mysterious. Let’s take a closer look.
10 - 15% estimate rule
Most car manufacturers will set the fuel light to come on when the amount of gas left in the tank falls to about 10 - 15% of the tank capacity. So if your car's fuel tank holds 45 liters, the light may come on when there are about 4.5 - 5.4 liters left.
This shows that when the fuel warning light is on, it does not mean that your car is "about to die" but is simply a red warning zone to let the driver know that the fuel level is low or about to run out of fuel.
Although the fuel light works on the same principle, not all vehicles are programmed the same. The make, model, and especially the size of your gas tank will affect how far you can go when the light comes on.
For example, the Mazda CX-5 has a 58-liter fuel tank, the warning light usually turns on when there is about 9.5 liters left, enough to go about 65 - 80km. Meanwhile, the large pickup truck Ford F-150 has a 137-liter fuel tank, the warning light usually turns on when there is about 11 liters of fuel left in the tank and the car can go about 50 - 65km, depending on the engine (V8 or EcoBoost).
Or Honda Civic has a smaller tank capacity of 47 liters. When the light is on, the car usually has 6.5 - 7 liters left, allowing it to continue running for about 50 - 65km if driven calmly.
How does a car measure fuel level?
Sharing with VietNamNet, auto engineer Nguyen Ngoc Thang - Director of Auto i-Tech service center (Tay Ho, Hanoi) said that modern car models use a fuel sensor, usually a float attached to a resistor in the fuel tank. When the fuel level drops, the float also drops, changing the resistance value. When it reaches a certain set level, the central control system will activate the fuel warning light.
"Some cars also have a system that estimates the remaining distance based on the most recent average fuel consumption. However, don't trust that index too much because what the car calculates is just a reasonable guess, not absolutely accurate," engineer Thang shared.
Why shouldn't you wait until the warning light comes on to fill up your tank?
Mr. Thang also pointed out that when the fuel warning light comes on, the remaining travel distance can decrease rapidly if the driver has to drive in heavy traffic conditions, slow down and stop continuously. In addition, driving urgently at high speed or driving on mountain passes also affects the estimated remaining distance. Therefore, even if there are still about 50 - 60km left, the driver still needs to be careful and not risk driving too far.
In addition, the director of the Auto i-Tech service center also emphasized: "Regularly leaving the fuel tank nearly empty not only increases the risk of getting stuck on the road, but also damages and fails the fuel pump, which is an important and expensive part of the vehicle's fuel supply system."
The reason is that when the fuel level is low, the fuel pump system will overheat because it is not submerged in fuel to cool. At the same time, dirt at the bottom of the tank is easily sucked up, clogging the fuel filter, affecting engine performance. This will potentially cause serious damage to the car engine.
When the fuel pump system fails, the cost of replacement will not be cheap. For popular cars, the price of a fuel pump will be from 3 to 10 million VND (gasoline engine) and from 5 to 20 million VND (diesel engine). For luxury cars, the cost of a fuel pump will be up to tens of millions of VND. Not to mention, if the engine has problems, the repair will be much more expensive.
"Instead of waiting for the fuel warning light to come on, make it a habit to fill up your tank when the fuel gauge shows about 1/4 of the tank left. That is a safe level for both the vehicle and the driver's psychology," engineer Thang recommends.
This not only helps prolong the life of the fuel pump, reduces the risk of damage, gives you peace of mind and avoids running out of gas on the road.
