The design of their engines differs. Unlike gasoline engines, diesel engines do not have spark plugs. Diesel engines are designed to have a more severe compression of the cylinder contents during the compression stroke. This results in much higher heating of the contents. In fact, the temperature becomes so high that the ignition of the fuel and air becomes spontaneous. Also, diesel engines have this highest thermal efficiency of any combustion engine, either internal (like in vehicles) or external (usually non-vehicular).

As a result, their fuel is also a little different. In the technical sense, the difference between gasoline and diesel fuel is the length of the carbon chains. Gasoline and diesel are both types of hydrocarbons (molecules made of hydrogen and carbon). However, diesel has longer carbon chains.

For those of us without chemistry degrees, this means that diesel is harder to ignite at ambient temperatures and needs more compression to ignite. Gasoline evaporates at ambient temperatures, but ignites most efficiently with a spark. It can also ignite under compression, as well. Mazda has plans to roll out an engine that utilizes compression, the Skyactiv-X, in 2019. Diesel was formulated to create more power for heavier vehicles, who rev less. Whereas, gasoline is formulated for lighter vehicles who rev more (go faster quicker).

Written by:

Beckie Bean

Digital Content Manager

December 11, 2017

Sources: Chemistry Stack Exchange, Car Buyer UK, Wired

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