Reference point
Stand beside a fuel station while a truck is filling up.
Do this before you read on. An entry only works when you have just smelled the thing.
Heavy, oily, with a waxy note and a faint layer of smoke. It differs from petrol in evaporating much less and clinging to everything.
This entry belongs to modern life: nobody teaches it, yet everyone recognises it. It is the reference for the whole group of heavy petroleum smells.
Hot asphalt belongs to the same group but is denser, with an added burnt note.
How to smell it
Stand a few metres from the pump, downwind. Smell. Then compare it with the smell of petrol at the same station — petrol is sharp and fast, diesel heavy and lasting.
Why this one is hard
Because all petroleum smells are lumped under one word, “fuel”. Separating them takes deliberate smelling somewhere both are present.
Don’t confuse with
This entry
Diesel fuel
Smoky & Mineral family
Diesel is an evaporating liquid; asphalt is a molten solid, so it has an added burnt note and is heavier.
Scientific note
Diesel consists of longer hydrocarbons than petrol, mostly twelve to twenty carbons. Longer chains mean higher boiling points and slower evaporation — that is the whole sensory difference between the two fuels. Diesel also contains some aromatic hydrocarbons such as naphthalene, together with sulphur compounds — the source of its characteristic pungency.
In Vietnamese life
The smell of diesel goes with bus stations, wholesale markets and the boats of the Mekong Delta. For many people who grew up on the waterways, the sound of an engine and the smell of diesel are an inseparable pair.