Petroleum-derived diesel contains about 75% alkanes and cycloalkanes, and 25% aromatic hydrocarbons. The average chemical formula for common diesel fuel is C12H23, ranging approximately from C10H20 to C15H28.
USE IN VEHICLES
Unlike petroleum ether and liquefied petroleum gas engines, diesel engines do not use high voltage spark ignition (spark plugs). An engine running on diesel compresses the air inside the cylinder to high pressures and temperatures (compression ratios from 15:1 to 21:1 are common); the diesel is generally injected directly into the cylinder near the end of the compression stroke.
The high temperatures inside the cylinder cause the diesel fuel to react with the oxygen in the mix, heating and expanding the burning mixture. This moves the piston. Glow plugs are used to assist starting the engine. Diesel engines are generally more efficient than petrol engines of similar size. Diesel engines also provide more torque and are less likely to stall.
A disadvantage of diesel as a vehicle fuel in cold climates is that its viscosity increases quickly as the fuel's temperature decreases, turning waxy at around 32F or just below. At this point the engine either will not start, or stops. Additives can help, but starting a diesel engine in very cold weather may still be difficult. Any additives must be added before the 'cold snap'.
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