What are car exhaust fumes made up of?
Mostly carbon dioxide, if the engine is tuned properly. The nitrogen in the air going in mostly comes out unchanged, but less than 1% of it is combined with oxygen to make various nitrogen oxides. (There are several.) Some of the carbon in the gasoline does not burn completely, so you get some carbon monoxide (maybe around 3%). Gasoline is a complex mixture of hydrocarbons, but I think it averages out to something like 8 carbon atoms and 18 hydrogen atoms. (In a straight chain, that is octane.) So gasoline would contain about 96 grams/mole of carbon and 18 grams per mole of hydrogen. During combustion, the carbon and hydrogen get oxidized (oxygen molecular weight = 16). So for each 114 gram mole of gasoline that was burned perfectly, it would yield 352 grams of carbon dioxide and 162 grams of water vapor. You also have to consider that water vapor is not really a pollutant, and most of the carbon monoxide and un-burned hydrocarbons can be oxidized to carbon dioxide in a catalytic conve
