Diesel vs. Gasoline Engines: Understanding Performance


GMC's commitment to professional grade engineering means that all GMC engines are designed and manufactured to precise standards. You have a choice of engine types in many of the GMC vehicles on the market. Understanding diesel vs. gasoline engine operation, fuel efficiency, and performance will help you make the best choice for your driving needs.



GMC engines, like almost every large engine, use a four-stroke cycle:


  • The first stroke is the downward movement of the piston, which draws the fuel mixture into the combustion chamber
  • As the piston moves upward for the second stroke, it compresses the fuel mixture
  • The third stroke is the power stroke; the fuel is ignited, forcing the piston down
  • Finally, the fourth stroke completes the cycle; the piston moves up, forcing the exhaust gases out of the cylinder


The main difference in diesel vs. gasoline engine operation is that diesel engines use a much higher fuel compression ratio.



Diesel engines are known to provide higher fuel efficiency. Diesel engines use a higher compression ratio, and, when running properly, the thermodynamic efficiency may provide up to 30 percent higher efficiency. With engineering advancements, however, both types of engines have greatly improved. GMC's turbo systems, Variable Valve Timing (VVT), and direct injection can produce significant advances in fuel efficiency.



Turbo charging and other refinements to diesel technology have improved cold-starting performance. Direct injection allows for starting within 3 seconds at temperatures as low as -40 degrees Fahrenheit. Improvements also have been made to the lack of acceleration that was experienced.


Diesel engines may require less maintenance compared to gasoline engines. It is critical to performance to have the oil changed at the recommended intervals. Diesel engines produce soot that can reduce performance if the system is not cleaned.



If you want a diesel engine, you can get one in a GMC Savana and Sierra 2500HD or Sierra HD. The Duramax diesel engine is available in the Sierra 2500HD Denali and 3500HD Denali. Gasoline engines are available in the Yukon series, XL 1500, XL 2500, and Yukon Denali, and in the GMC Terrain, GMC Sierra K15, C15, and 15. Gas-powered engines are also available for GMC Savana 3500, 2500, and 1500, as well as the Acadia.


The Duramax LML and LGH engines can also run on biodiesel. Biodiesel is a mixture of petroleum diesel and biodiesel created from renewable resources.