We’ve all been there. You’re driving, when your low-fuel light comes on and you think, “I can get home; I’ll do it tomorrow.” Or maybe you decide to keep driving until you find cheap-enough gas. It makes sense, your car will continue down the road for a while longer … but at what cost? Is consistently driving with the gas light on really that big a deal? It turns out it kind of is.
Miles to Go Before I Fill
First off, you don’t really know how much farther that remaining fuel will take you. Even with the very accurate volume measurements in modern cars, mileage is still an estimate. It depends on your driving habits, traffic conditions and even things you wouldn’t think of like tire inflation.
The point is that nothing is promised, and that alert is meant to warn you to fill up ASAP. Getting stranded on the road isn’t just a nuisance — it’s dangerous. Plus, imagine the moments before the stranding, as your engine shuts off while you’re cruising down a busy highway. Not great!
Aside from the dangers posed to personal safety, running your tank on low is bad for the fuel pump. This should concern you, because fuel pumps aren’t an easy repair on most vehicles. Many are located inside the tank itself, demanding a labor-intensive replacement process.
Fuel pumps are also cleverly designed to use the fuel running through them for heat dispersal. When your gas runs low, the pump takes in more air. This generally makes the pump work harder, simultaneously heating it up and removing the only help it had to cool down. Over time, damage will accrue and lead to early fuel pump failure.
Suck It Up
Older vehicle models have metal tanks that generate small particles of rust, which settle on the bottom of the tank. These days, most tanks are made of plastic, but their floors are still a place where contaminants build up. Continuing to drive after the fuel light illuminates your dash sucks fuel from this murky area, which can block the fuel filter. This can restrict flow, cause the pump to work harder and affect performance. It can also allow particles to make it through to the engine, causing other damage. Additionally, incorrect air-to-fuel ratios can wreak havoc on your catalytic converter over time. Driving on low fuel is even worse for a diesel engine, as pulling air into it seriously affects performance and requires a lot of work to right.
A good general rule to avoid prematurely replacing your fuel pump is to keep your tank over a quarter full. It just requires a change in perspective — imagine the quarter mark is the low gas light instead.
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Photos courtesy of Blair Lampe.
Blair Lampe is a New York-based professional mechanic, blogger, theater technician, and speechwriter. In her downtime she enjoys backpacking wherever her boots will carry her, rock climbing, experimental theatre, a crisp rosé , and showering love on her 2001 Sierra truck.