[John Chapman (OP)]

The water cycle is well known. Water evaporates into the atmosphere, condenses into fine droplets, precipitates as rain and then evaporates again. But what about petrol (gasoline)?

There must be huge amounts of petrol vapour evaporating all over the place. Where does it all go? Why don’t we have petrol clouds? Just imagine the effect of lightning in a petrol cloud!

And what about alcohol vapour? Why aren’t the fish permanently in party mode because of all the alcohol raining into the rivers? And why doesn’t the alcohol preferentially evaporate to produce more alcohol clouds. And so on…
 

[paul.fr]

Why don’t we have petrol clouds?

You sort of do, acid rain.

[John Chapman (OP)]

Aah, that's not the same thing. As far as I know (and I could well be wrong) the clouds themselves aren't acidic but the rain picks up carbon particulates on the way down which dissolve in the raindrops and produce weak carbonic acid.

But all this petrol vapour in the air must be going somewhere. It strikes me there can are only two possibilities: either there is some other mechanism removing it or it accumulates to the degree that it must eventually condense into petrol clouds. Since patently we don't have petrol clouds, where is the petrol vapour going?
 

[Bored chemist]

The effect of sunlight and oxygen on most organic compounds means that they get destroyed or converted to something soluble in water ans washed out by the rain.