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 FAQ #38
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What is the difference between Petrol and Diesel
Diesel fuel (Diesel Oil).

If you have ever compared diesel fuel and petrol, you know that they are different. They certainly smell different. Diesel fuel is heavier and oilier.

Diesel fuel evaporates much more slowly than petrol -- its boiling point is actually higher than the boiling point of water. You will often hear diesel fuel referred to as "diesel oil" because it is so oily. .

Diesel fuel evaporates more slowly because it is heavier. It contains more carbon atoms in longer chains than petrol does (petrol is typically C9H20, while diesel fuel is typically C14H30). It takes less refining to create diesel fuel, which is why it should be cheaper than petrol...but we know we are being fleeced

Diesel fuel has a higher energy density than petrol. On average, 1 gallon (3.8 L) of diesel fuel contains approximately 155x106 joules (147,000 BTU), while 1 gallon of petrol contains 132x106 joules (125,000 BTU).

This, combined with the improved efficiency of diesel engines, explains why diesel engines get better mileage than equivalent petrol engines.
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FAQ Posted by j-c
Info Created: 25 April 2007
Last Updated: 25 April 2007