There’s the oil from the oil wells which is inflammable but it’s not in the form of petrol or diesel, which is also decided from the same oil, but petrol isn’t oily to the touch the way regular cooking oil is. But cooking oil isn’t as inflammable, irrespective of whether it comes from sunflowers, or groundnuts, or coconuts or some other source. However, the oil on our skin is oily, but again not inflammable.
Help me wrap my heart around all these different ‘oils’ – and why some are more oily to the touch vs those that are not, and why some are inflammable vs those that are not.
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In a nutshell, you start with a molecule called a “hydrocarbon” which is essentially a carbon atom with a bunch of hydrogen atoms linked to it. Carbon/Hydrogen molecules are quite stable which is nice, but both elements prefer being bonded to Oxygen. So if you give them access to a tiny bit of energy (heat) and some oxygen they’ll break the bonds and form Water (H20) and Carbon Dioxide (C02).
Now if you can start chaining more carbons and hydrogens together to get longer and longer molecules. Because chemists are naming geniuses; you tell how many carbon atoms are in a given hydrocarbon chain by it’s name, methane has (1), propane has (3), Butane has (4) carbons, Pentane has (5), hexane has (6), Octane has (8), diesel has (12), and on and on.
In general the lower carbon molecules, like methane and propane, are highly combustible gases. The mid-to-higher single digit molecules are highly combustible liquids, once you get into the diesel zone though the molecules become increasingly stable.
For example, if you light a match in a room filled with methane, you’re in for a bad time. If you light a match in a room full of gasoline vapor, you’re in for a bad time. But you can actually put out a match in liquid gasoline as it’s fairly stable (DO NOT TRY THIS), and diesel fuel can actually *put out* fires, you have to compress it first to use it as fuel.
This trend goes all the way to home heating fuel and ship fuel (so called “Bunker Fuel”) which is essentially sludge.
The point being that natural oil deposits contain a wide variety of all of the above hydrocarbons. While some might be heavier on methane and others lean towards heavier diesel, they are a blend. Before raw oil can be sold to the consumer as fuel it needs to be processed to separate the various gases and liquid fractions, which may even go on to receive further processing and separating for the consumer market.
Per your prompt, cooking oil isn’t inflammable, just google “home oil fire” and you’ll learn that it’s very, very much so flammable, it’s just stable to higher temperatures. Considering the above trends, most cooking oils are in the (18) carbon-and-higher range making them quite stable. But consider that cooking oil can be repurposed as bio-fuel, it’s actually not that far off from diesel in that regard.
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