People will tell you not to get back in the car, because it's dangerous. What's really dangerous is that potential static buildup getting in and out, which can discharge when you touch the nozzle.
If you do get in and back out, make sure to ground yourself by touching the bare metal of the pump itself before you grab the nozzle. It's not perfect, but it's much safer than not taking the time to ground at all.
Is there data on this? I have never heard of this happening and I imagine there are millions of gas pumping events per day (or at least hundreds of thousands) where a person sets the nozzle, sits in the car, then comes back out.
Compared to all the other risks of cars and gasoline, the relative risk seems miniscule.
from back in 2008 "the Petroleum Equipment Institute, a trade group, found that there were at least 170 static electricity fires at gas stations from 1992 to 2006. Considering that the American Petroleum Institute estimates that there are 11 billion refuelings in the United States a year, the problem probably isn’t a big one." from https://www.nytimes.com/2008/07/27/automobiles/27STATIC.html
I'll note that in the state I live (MN) it's technically illegal to get back in your car while pumping (you have to be " in close attendance to the dispenser nozzle").
I know for certain I've discharged static electricity by touching metal of my car after getting in/out, or cleaning out trash, etc while the pump runs.
Would that little spark be enough to ignite the vapors? I have no earthly idea.
A few years back Richard Hammond (the short former Top Gear UK) presenter did an experiment with this on another British show of his called Braniac (a sort of light entertainment popular science show) where he filled a caravan with petrol and fumes and attempted to get it to ignite through static electricity (they did lots of different ways of generating it).
They couldn't do it and even when for the laughs they decided to blow it up with a match it still didn't ignite.
The fuel air density has to be a certain ratio. This is why you have complicated systems to inject just the right amount of air and gasoline into the pistons. I would guess that since it is much harder to combust liquid gasoline is would be much harder to combust a very heavy gas/air combo.
Probably best to not use entertainment shows as a metric for safety.
You're supposed to stand by the pump so in case it doesn't shut off you can shut it off manually. You're responsible for spills, so you don't want to be sitting in your car while gallons of gasoline pour out and run under and around it.
