When planning a big trip, it’s common practice to work out how much fuel you’ll need to avoid having your fuel light come on while you’re on the road. However, you can’t plan for everything.
As soon as your fuel reserve light comes on on your dashboard, you’ll know that you’ll only be able to drive a few more kilometres. But how many? And does driving when your fuel light’s on produce more consequences for your car or wallet?
Keep reading the article to find out the myths and truths about driving with your fuel light on.
What is a car’s fuel reserve?
A car’s reserve is the minimum amount of fuel it should have in its tank, as recommended by the manufacturer, to ensure proper car operation. It’s a precautionary measure to prevent the engine from stopping due to a lack of fuel, giving the driver the chance to find a petrol station before this happens.
Vintage cars contained a secondary tank that stored the extra fuel when the vehicle reached the reserve.
This “extra tank” is now incorporated into the main fuel tank.
What is the Volume of a Fuel Tank Reserve?
The amount of fuel held by the reserve depends on the model of the car in question, but as a general rule, it is assumed that when the tank reaches the minimum fuel, this will vary between 5 and 8 litres.
When is a Car’s Reserve Setting Activated?
A car will generally reach its reserve when the fuel in the tank drops down to about 10-15% of the total tank capacity.
How many Km Can You Drive with your Car in the Reserve?
When it reaches the reserve, your car’s low fuel light comes on, warning you to refuel.
The number of kilometres you can travel under these conditions varies greatly depending on the model and engine of your vehicle.
Are there Differences Between Driving with Low Fuel in Petrol Versus Diesel Cars?
Avoiding allowing the reserve fuel to run out is essential, both for petrol and diesel engines.
In petrol engines, driving with low levels of fuel can lead to impurities in the tank, damaging the injectors or pump.
This situation means the engine has to work harder, and, as a consequence, the aspiration will not be done correctly, creating bubbles in the circuit. This could lead to the engine circuit getting very hot and even result in engine damage.
Where diesel fuel is concerned, air can get into the engine circuit and injection system, making it impossible to restore normal starting pressure.
Is Driving with Your Fuel Light On Bad?
Yes, especially if you do it often.
As with other issues, if this only happens sporadically, it won’t be a problem. However, if you frequently postpone your stops at the petrol station and almost always drive in the reserve, you may be damaging your car.
What are the Risks of Driving with Your Car Fuel Light On?
The main risk is facing high repair costs, which can be inconvenient. These unexpected expenses can arise due to two situations:
Residues and Impurities
In old car models, fuel tanks were made of metal, so when the inner walls dried up, they would rust.
Currently, more recent models are fitted with tanks made of special plastic that does not get damaged or rust. However, over time, the fuel begins to gain sediment that accumulates at the bottom of the tank.
If you always fill your tank before your fuel light comes on, the sediment settles at the bottom and does not reach the fuel pump or supply circuit.
If you often drive with the fuel light on, your car’s pump may end up clogging the fuel filters or other injection system components.
Fuel Pump Stress
When your fuel light comes on, your fuel pump has to work harder, especially when going up or down hills and around curves, as the fuel is moved around the tank during these manoeuvres.
When working under stress, the pump overheats, leading to further wear.
Ignition Problems
The pump sends the pressurised fuel to the injectors. When the fuel level drops, the pressure in the system also drops, leading to ignition failure and a drop in engine performance.
Catalytic Converter Damage
In more serious situations, driving with your fuel light on can lead to improper combustion in the engine.
This can overload the catalyst, causing damage to the vehicle that can be very expensive to fix.
Do Electric Cars Have a Reserve Tank?
Electric cars aren’t fitted with a reserve tank because they run on batteries. In fact, many models recharge their batteries using the car’s own brakes.
Similarly to combustion cars, electric cars have a display that indicates the charge level and approximate range, informing you whether you need to find a charging station as soon as possible or not.
As you can see, it’s no myth that driving with your car fuel reserve light on is a myth, especially if you do so regularly.
If your fuel light is regularly on, you may be wearing out and damaging your car unnecessarily. Avoid this situation and prevent damage before it’s too late.
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