Diesel engines can be made to run on a wider range of less-volatile fuels than a gasoline engine. True or False?

• A. False
• B. Not sure
• C. It depends
• D. True

Answer: (D)

Diesel engines rely on compression ignition, injecting fuel directly into very hot, compressed air. Because the fuel doesn’t need to vaporize before mixing with air, the engine isn’t as sensitive to fuel volatility as a gasoline engine is. Gasoline engines depend on a volatile fuel that readily forms a combustible air-fuel mist; if the fuel is too non-volatile, it won’t vaporize properly and combustion becomes unreliable. That means diesel engines can tolerate a wider range of less-volatile fuels, such as heavier distillates or kerosene-type fuels, and still ignite and burn efficiently. Of course, other fuel properties like cetane rating and lubricity matter, and some fuels may require modifications or specialized injectors, but the fundamental idea is that the way diesel combustion works gives it broader fuel flexibility. Therefore, the statement is true.