What's with people filling their gas tanks with their engines running? Is it really not that dangerous?

Dear Car Talk

Dear Car Talk | Sep 01, 1998

Dear Tom and Ray:

Help me out here. I need to know if I have to start wearing my flameproof
sweater next time I fill up at the neighborhood gas station. The last two times
that I filled up the tank at the local gas station, there were Richard Petty
wannabes filling up their cars with the engines still running.

Now, I know illiteracy is bad in this country, but do people really not
understand the words "turn off your engine while refueling"? I was going to ask
this soon-to-be-Roman candle whether he thought it was OK to ignore the signs,
but I decided to ask you guys instead. Should we pay attention to these signs,
or should we all just ignore them? -- James

RAY: Of course we should pay attention to these signs. After all, someone spent
all that money to print them up, didn't they? It's the least we can do.

TOM: Here's why we should obey the signs. When you're refueling a car, gasoline
vapors are generated. And there's always a possibility that gasoline will spill
and vaporize.

RAY: And when gas vapors meet a spark, the result is ... kaboom! So it makes
sense to do everything possible to reduce the chances of blowing yourself and
other innocent people into the big filling station with clean restrooms in the
sky, right?

TOM: And while random sparks are not normally created by most cars, it can
happen. If you had a bad spark-plug wire, for instance, and the spark was
jumping, under just the right (actually wrong) circumstances, it could ignite
the vapors and take you and all those S&H green stamps with it.

RAY: On the other hand, when the engine is off, there's almost no chance that a
spark will ignite the gasoline fumes. So why not cut the risk to zero? Are we
that lazy that we can't shut off the engine for five minutes while we refill the
gas tank?

TOM: And by the way, James, for the same reason, you should also insist that
your mother-in-law snub out her El Producto before you send her out to fill the
tank, too.

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