When it comes to automotive myths they all have a slight grain of truth to them, and so it is with this one. So, is it dangerous to refuel with the car engine running?

THERE HAVE BEEN plenty of TV show myth busting stories done on this one… I remember watching one with Richard Hammond (Brainiac) years ago where he stashed a bunch of mobile phones inside a caravan filled with open petrol cans to see if there was enough ‘spark’ from a phone to ignite the petrol fumes. But it didn’t. They ended up blowing up the caravan for dramatic effect, but it wasn’t the phones that caused the explosion. It was static electricity generated via nylon clothing…watch the video below.

Sure, there are signs warning against mobile phone use while refuelling but the problem is that mobile phones aren’t designed to produce a spark, although you require bugger all of the energy stored in a fully charged mobile phone battery to make a spark, about one five-millionth. Of all the petrol station fires recorded, static electricity was generally deemed to be the overwhelming culprit, and that’s got nothing to do with your mobile phone. But it does have everything to do with your clothes and whether the earthing terminal on the petrol bowser is broken as is shown in the Brainiac video…but that would be very rare.

The Australian Mobile Telecommunications Association said, “there is no sound technical basis to prohibit the use of mobile phones at petrol stations or single them out as hazards”. It has cited a number of other sources to defend its claim, like Shell Oil UK which looked into the potential risks in 1991 and found, “…portable cellphones properly used do not represent a meaningful hazard on the retail forecourt. Without doubt, apart from the human acts of smoking and striking a match, the thing that represents the greatest hazard on the retail forecourt is the motorcar!”

So, using your mobile phone while filling up cause an explosion at a petrol station. The signs are mainly there to encourage everyone to concentrate on what they’re doing at the time and that’s good advice. Okay, one myth busted. Hang on…if anyone tries to argue about the Shell email citing the dangers of mobile phones and refuelling your car, don’t, because that email was a fake. Moving on.

So, what about refuelling while the engine is running… Well, petrol vapour will only combust within a very narrow range which is 2-8% of the volume of air. If it’s less than 2% there’s not enough petrol vapour to combust and if it’s more than 8% there’s not enough oxygen to combine with the vapour, so, again, it won’t combust.

But, with the engine running, there are plenty of spark producing items, like the spark plugs but these are only a problem if the insulation has broken down, but then they’re unlikely to work properly, so… and then there’s the starter motor but it’s usually buried deep in the engine bay where oxygen and petrol vapour can’t reach it in the right concentrations.

And don’t forget that while your refuelling your car there are other drivers pulling up behind you and beside you and they don’t cause a fire… and then there are the cars driving past the petrol station.

But let’s not forget that most petrol stations are required to have Vapour Recovery technology fitted, and in the Sydney metro area this has been a requirement since 1986 and it was expanded in 2010. There are similar requirements across the country.

The petrol stations are required to have capture devices both on their storage tanks and on the bowsers. While this is intended to stop vapours from entering the atmosphere and contributing to pollution, it also helps to ensure the concentration of petrol vapours at petrol stations is below the concentration levels required to start a fire.

But, like not using a phone while refuelling it is good practice to switch off the engine. It means someone can’t steal your when you head inside to pay for fuel, and so on.

While you required to switch off your car while refuelling there are plenty of places where this rule is ignored, like in particularly hot countries where locals will leave their car running with the air-con on full to keep everyone inside nice and cool.

So, while there’s the potential for your running engine to start a fire at a petrol station, it’s highly unlikely.