We all know that running your car out of fuel is a bad thing for obvious reasons like the fact that it can leave you stranded. There’s also a good chance you’ve also heard that running on empty can cause damage to your car. But what actually happens?
This video by Engineering Explained dives deep into the topic in full in the following nine-minute video. And it’s pretty damn fascinating. We’ve talked about this topic before, but sometimes it’s good to have another visual.
Obviously, an engine needs four things to function: oxygen, a spark, compression, and fuel. Without one of those things, it shuts down, and you’re not going anywhere. There’s no longer combustion.
The most obvious part of your car that’s affected by running out of fuel is the fuel pump. Instead of sucking up your gas, it’s suddenly sucking up a bunch of air. Fuel pumps are designed to be simultaneously cooled by the fuel as it’s sucked through the pump on its way to the fuel injectors. Replace the fuel with air, and your pump starts to get hot. That’s obviously not good.
However, running out of fuel means that the engine no longer works. So it shuts off. The amount of time the fuel pump is pulling air and heating up is minimal. But that’s in an idling scenario. If you’re out there aggressively driving around, braking hard and making hard turns, the gas in the tank is sloshing around. In that case, it’s possible that the fuel pump can start sucking up hot air while there’s still technically still fuel in the tank because the fuel isn’t necessarily always on the bottom of the tank. That’s not terrible in and of itself. But if you’re doing that a lot, then the fuel pump is frequently getting hot and thus wearing out.
Which brings us to the engine itself. What’s the impact on the engine?
The video notes that impacts on the engine usually rely on some unique scenarios. Misfires can happen if gas doesn’t make it to all the engine’s cylinders—but it’s still rare that that could cause damage. If you’re driving really hard, though, there’s a chance that your engine isn’t running at the proper air:fuel ratio and therefore is getting hot.
Overall, it’s pretty rare that just running low on fuel will end up damaging your car. If you only do it once or twice, you’re not particularly likely to have any super detrimental effects. Run out of fuel often though, and you risk doing damage to essential components of your engine. Anyone who has had to replace a fuel pump can tell you, it’s not cheap or easy.
It’s always better to be safe than sorry. Fill up your dang gas tank when it gets low and don’t drive like an asshole.