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KingSpork t1_ja6m5c2 wrote

Reply to comment by ECatPlay in If the fuel that goes in car engines is extracted from hydrocarbons, which consist of only Hydrogen and Carbon, and those hydrocarbons react with Oxygen in the air (combustion reaction), to produce CO2 and H2O, why do we get a bad smell from car exhaust fumes if both gases are odorless? by Protoflare

So does this mean that car exhaust smelled different pre-catalytic converter?

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ECatPlay t1_ja6pex2 wrote

Oh, yes. In particular, some refineries blended extra aromatics in with the gasoline to increase the octane: benzene, xylenes, and alkylates. And before catalytic converters and emission standards limited unburnt hydrocarbons in the exhaust, these could give it an almost pleasant odor, especially when it was running rich. (After all, benzene compounds get the name “aromatic” because of the type of odor they have.)

But only if the engine was burning clean and not also burning oil. That made the exhaust smoky. Now days engines are manufactured to closer tolerances and you seldom have to add oil. But back in the day it was routine to check your oil every time you stopped for gas, because there was always a little bit of oil making it past the rings and getting burned in the cylinders.

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trapperjohn3400 t1_ja7n8o7 wrote

Yes it could vary from a light, sweet smell, to a horrible acrid smell. But they were all quite smelly. It made driving in stop and go traffic in a city very, very unpleasant.

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