Is it bad to run your vehicle when it’s low on fuel?
Tuesday, 27 August 2019
There's nothing worse than jumping in your car when you’re running late for work and seeing the dreaded fuel light come on.
Cursing your past self who said, ‘I'll fill up tomorrow morning on the way to work’ but then proceeded to stay up into the early hours binge-watching ‘The Office’ for the 15th time, you wonder if you can risk driving all the way without stopping.
Running out of fuel is one of the worst experiences you can have as a vehicle owner, but it’s almost a rite of passage for it to happen at least once in your motoring lifetime.
But can it cause damage to your vehicle, or just your ego?
First, we need to look at the fuel system and understand how it works.
On modern fuel injected vehicles, both petrol and diesel, the main fuel pump is located inside the fuel tank.
It is located almost at the bottom point of the tank, usually in a swirl pot (a square-looking device that keeps the fuel pump submerged even when cornering to prevent stalling) or fitted inside a Modular Reserve Assembly (MRA) unit.
These units are designed to keep the fuel pump submerged at all times as the fuel acts as a cooling system and lubricating system to keep the pump operational.
With that out of the way, just how exactly is running low or out of fuel bad for your vehicle?
When the tank is run dry, the pump runs without lubrication or cooling which can cause damage over time.
While it may not cause the pump to fail if it happens once, running the pump dry multiple times will cause it to overheat and fail, and replacement is the only option.
On older vehicles, the fuel tank was made from pressed metal.
Constant contact with petrol and other contaminants would cause the inside of the tank to rust away with sediment settling down near the fuel pump.
When the fuel tank is near empty, this sediment tends to be picked up by the fuel pump and can damage the internals of the pump and clog the fuel filter.
When this happens, replacement of the fuel pump and filter, as well as cleaning out or replacing the fuel tank, are the only options to get you back on the road.
Thankfully, most fuel tanks these days are made from plastic which has greatly reduced this issue.
However, sediment can still be present from contaminated fuel, poorly sealing fuel caps and various other sources, so it’s best to keep an eye on the fuel level and refill before the fuel light comes on.
If you have a diesel vehicle, running low or out of fuel can be a much more troublesome experience.
Due to the high pressures associated with diesel fuel injection, running the fuel pump and lines dry can cause expensive damage to both the diesel injection pump and the diesel injectors.
Once the fuel tank has been filled again, the whole fuel system must be primed to remove all traces of air, otherwise poor running, stalling and other issues can arise.
So, yes, running your vehicle low on fuel can be bad, especially if you run it completely dry and most manufacturers recommend refuelling the vehicle once the needle goes below ¼ on the fuel gauge.
So, next time you notice the fuel gauge reading near empty but you’re already pulling into your driveway for the night, think about heading back out to the service station to fill up.
Alternatively, leave it for the morning but get up early enough to leave yourself time to carry out this essential chore.
Staying up till the early hours watching The Office may be fun, but it ain’t no laughing matter when you’re not only late for work but conked out on the side of the highway.
Or if you are staying up late, you should check out these 7 tips to increase your fuel economy, or find out how far you can really drive with your fuel light on. When you do go to fuel up, make sure you've got one of these apps which helps you find the right fuel price!
Finding a passion for cars from a young age, Joel carried out work experience as a mechanic whilst at school before starting an apprenticeship after finishing year 12.
After almost 10 years on the tools and in customer service, he moved into the IT realm as a Data Analyst and In-House mechanic at AutoGuru.