Can You Pump Gas With The Car On And Other Curious Gas Station Questions

Offbeat / 16 Comments

Here's what you need to know to stay safe while performing the regular duty of a fill-up.

It's a little odd that filling a car with gas isn't covered by the driving test (in the US, anyway), as petrol is combustible, and you see people doing stupid things. What gets forgotten is that it's not the liquid fuel that's the biggest issue; it's the fumes. You can drop a match into gasoline (but you shouldn't), and the liquid will simply extinguish the flame unless it has time to combust the petrol's vapor as it drops. Gasoline needs air to burn; hence a car's ignition system measures the air-to-fuel ratio ready for the spark to ignite it. That's why if you see someone smoking on a forecourt, you should go to the next station. It's not visible fuel leaks that are dangerous at a gas station. But that doesn't mean other things are inherently unsafe, despite the warnings. So, let's answer some common questions here and dispel some gas station myths.

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Can You Pump Gas With The Car On?

You can pump gas with the car running, but it isn't recommended. A gas tank doesn't need to be sealed or maintain pressure for the fuel pump to do its job. Race cars do it all the time, but that doesn't mean we should. The real question is, is it safe to pump gas with the car running?

Having the engine warning light come on because the ECU senses a lack of pressure in the gas tank and thinking you forgot to seal the gas cap isn't dangerous. The danger put forward (according to the Petroleum Equipment Institute) is that a car could build enough heat and electricity to ignite vapor. It's also noted that this happening is rare but not unheard of.

The big ole electric starter motor under the engine you use to start the car back up suddenly draws anywhere from 125 to 300 amps, and vapor from the pump doesn't rise - it spreads.

So, can you leave your car on while pumping gas? Yes. Should you? No. We say just shut your car off like a sensible human being.

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Is Using A Cellphone While Pumping Gas Dangerous?

It used to be believed that sparks from a cellphone could ignite petrol vapor, but even the slightest scrutiny of that hypothesis shows that it's nonsense. If your cellphone is sparking, there's going to be a different sort of fire, and you don't have to be holding it in your hand for that to start. The reason it's forbidden, and there are "No Cellphone Use" signs up on the pumps, is down to safety insurance.

It's there for the same reason there are signs instructing that cars should not be left unattended while gas is being pumped. Yes, you could talk on the phone or walk away from the car and get a snack from the store, but if something goes wrong, you likely won't see it. If the automatic cutoff fails and the pump keeps going after the tank is full, it's a safety and financial hazard to be avoided.

When the TV show Mythbusters looked into the subject of cellphones, it observed that people leaning against the car and rubbing metal to build up static electricity is the danger, but from video footage, it tends to look like the phone is the culprit.

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Is It Dangerous To Get Back In Your Car While Pumping Gas?

There are two reasons not to get back in the car while pumping gas, no matter how cold it might be outside and how toasty and warm it might be inside your car. The first is that you're not watching over the process, but there's another safety element, and that's static electricity. When you get out of a car to pump gas, you should be touching something metal to ground any static electricity build-up. By getting back in and out of a car, the risk is building up a charge and then going directly to touch the pump that's now attached to your car while there's a real possibility of there being vapor around. So, yes, we would say it is dangerous to get in and out of a car while gas is pumping.

Is It Better To Fill Up With Gas In The Morning And At Night?

You might have an older relative that believes beyond the point of reason that filling up when the weather is colder, at night or early in the morning, gets more gas for the money. The theory is that petrol is denser when it's colder, so you'll get more fuel. While the science of heat and temperature on liquids holds water (pun intended), the gas you're pumping at the station is stored in containers wrapped in concrete about 15 to 20 feet underground so the fuel remains relatively stable at around 55 degrees. The only chance of taking advantage is just after the fuel has been delivered. Still, fuel temperature stabilizes quickly, and, for crying out loud, do people really think fuel companies haven't factored that into their storage, measurement, and dispensing equipment?

Does The President Control Gas Prices?

You might have seen the stickers people have been putting on fuel pumps of President Biden pointing at the price display and a speech bubble saying, "I did that!" It's pure propaganda, as no president, Republican or Democrat, directly influences gas prices. As with anything, what becomes politically charged often gets oversimplified to make a point that may not be accurate. Besides, President Biden likes to drive a Corvette, which is a car famous for gas-guzzling V8 engines. Even if he had control over the prices of gas, we doubt any car enthusiast would intentionally raise them.

A government can have an effect over time with its policies and legislation, but oil prices and corporate greed are the real contributing factors. Oil prices depend on supply and demand, and oil companies are under pressure to increase profits every year from board members and shareholders. That's why they are constantly testing what the market can bear, and fuel prices are forever trending upward in the long term. It also doesn't hurt the fuel industry when presidents are blamed for rises in prices, and it's worth remembering it's equally nonsensical when a politician takes credit for prices dropping.

Paul Weaver

Does Holding The Nozzle Lever Halfway Make You Pay For Air?

This is one of the most recent and dumbest myths out there. The conspiracy theory is that if you don't pull the nozzle's lever all the way quickly, you're paying for gas you're not getting as air is entering the system. As much as we detest the corporate greed of the fuel industry, that would be a fraud, and they are held to account by law over weights and measurements both nationally and on a state level. Plus, that's just not how fuel pumps work. An electronic meter in the pump measures the volume of gas - and just gas - flowing into your tank and at all rates of flow.

The next time one of these myths comes up, educate your peers. You could make them safer and smarter.

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