What happens if you keep the engine on when at a gas station?

If you live in the prairies during the winter you will see cars at gas stations running while get filled up. If it's -30 or -40 this happens a lot but people should not get in the habit. Here's also a reason to use quality engine lube synthetics so the engine doesn't have the problem starting if it -40 as it would with petroleum based engine oil.

Turning the car off eliminates many fire related possibilities. The running car is very electrical and this is how the fuel is ignited in the engine. The running car's exhaust is very hot and could possibly ignite a spill.
when filling a gas can it should be on the ground to ground any stray static electricity spark that could come from a defective gas pump. Cars also are not grounded. Tires are an insulator.
So what happens is your risk of danger is needlessly elevated. Mostly up to you. I just turn it off.

Beside it being a Federal law there is less of a chance the car will burn if there is a problem with your vehicle that you have no idea about. They also tell people not to sit in the car and then slide off the seat and grab the fuel nozzle because of the static spark exploding the fuel vapors coming out of the filler tube opening Now you know when you see idiots at the gas station.

There are gas fumes about and if the car emits sparks or flame from the exhaust or engine it might ignite the gas.
It was much more of a problem in the past.

I'm pretty sure that's also why there's a "no smoking" sign posted there too. As the liquid fuel pumps into the vehicle tank, the vaporized fuel in the tank is pushed out the filler neck causing a combustible vapor area by the fuel nozzle where there is oxygen present in the quantity to create an explosion by a spark or static discharge.

Add: Gasoline fuel truck tanker filling transfer station buildings by the tank farms have photo theory spark and flame detectors that will shut down the pumps on a spark and trip off the foam extinguishers if the flames are present.

Retired NICET certified alarm technician.

Usually there is percpitate in the tank such as rust when u add gas to the tank that percepitate float over the petrol so it wont damage the car but if your engine was on it will take water or rust to the engine which would be very harmful (noy my answer its a mechanic friend of mine)

Most of the sparks from static electricity will come from putting the nozzle into the fuel tank. it is very rare this will happen. Same thing can happen to a fuel can that is sitting in a bed of a truck or trunk. I drive a diesel and if the wife is with me I leave it running but by myself I don't because of car jackings

It's a safety issue related to the existence and buildup of static electricity near gasoline fumes. The main idea is to reduce the possibility of igniting fumes when you or others are fueling your automobiles. Your BIGGEST concern should be your cell phone. LEAVE IT IN THE CAR and away from your body when fueling. They alone are the single greatest danger of causing an explosion by a spark as well as static electricity from your body. Always touch your auto's metal 1st BEFORE beginning the fueling process. This should help eliminate any static off your clothing/flesh area's. This also applies to everyone with any form of cell phone. The total idea is to drastically reduce the possibility of static electricity buildup....aka sparks.

If a cop see's this he thinks Oh Boy money for my Judge. Stations don't like it as they think a drive off. If you take of fast with the hose in the tank others think why is that guy there smoking at the next pump. As the hose has a disconect & shut of but some gas spills first.

Not much it was done that way for the better part of a century. The concern has always been that a stray spark could ignite the fumes. It's overkill , reaching the concentration of vaporized gas in the engine compartment to reach flashpoint is next to nil.