A chemical reaction takes place in which oxygen from the atmosphere combines with the carbon in the gasoline (burning = oxidation). Oxygen that wasn't in the gasoline to begin with. Gasoline is mostly hydrocarbons, and hydrogen weighs considerably less than oxygen (source).
It bothers me, this clinging of different elements.
I don't think it's advantaged me or any of mine.
I've appealed to and been ignored by the usuals
I've appealed to the Orange, he sympathies