Why is it a law to shut off the engine before pumping gas in your car?
Re: Car gas
Because there is a danger of active sparks while engine is running and fuel is being pumped. It's the same reason why you're recommended to touch metal (either car body or pump enclosure) to discharge any static one maybe carrying, that could potentially start an instant fire as well.
Re: Car gas
coz government don’t like fireworks… 
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Re: Car gas
i pumped gas last week and totally forgot to shut off my car while doing it. then i saw the sign while i was driving out 
what could have happened? 
Re: Car gas
Well, it's okay. But it's highly recommended to shut off engine. Nowadays the nozzles are designed to eliminate fumes. But why take the chance?
What could've happened in case of leaving engine on? Dont know to be honest....Fire is one possibility!..