The biggest threat is low humidity combined with a static electricity discharge. So much humidity in many areas, particularly in summer, that it is probably not a real problem. However in areas of very low humidity, getting back in the car after starting the gasoline to stay warm, and then getting back out to finish can start a static discharge fire. Have seen videos of this, and it can be almost like an explosion. Leaving a gasser on during refulling can be against the law, but is likely no more risky than the above scenario. Diesels, on the other hand, can injest a vapor cloud and blow clear to the moon, as the air is already in the combustion chamber and HOT.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150