Gasoline vs. Diesel

In terms of application, diesel is most often used by heavy-duty trucks, semis, buses, boats, and vehicles which may require a higher torque rating and more low-end pulling power. Gasoline powertrains are most often associated with passenger cars, SUVs, and light-duty trucks.

Although they are both derived from crude oil, gasoline and diesel have different physical properties. Gasoline is much thinner and has a distinct odor. Diesel fuel has a thicker state of fluidity, almost like a lightweight oil. These physical differences come into play when diesel attempts to make its way through a gasoline vehicle's fuel system and engine components.

Diesel is also not as combustible as gasoline. Since each fuel has its own autoignition temperature, diesel and gasoline engines work differently. A gasoline engine utilizes spark plugs to ignite the fuel, while a diesel engine uses the pressure created by compression within the engine to ignite fuel (though a part called a glow plug might help when the engine is cold). In other words, diesel is heated up by being squeezed, while gasoline is lit with fire. Furthermore, gasoline is often mixed with as much as 10-percent ethanol, a highly flammable organic compound used as a biofuel additive. Ethanol makes gasoline even more combustible than it already is.

In short, gasoline and diesel engines are designed to operate using only their specific fuel-type and not the other.