Arguably the most legendary engine on this list, the X15 diesel engine from Cummins makes a solid 565 horsepower, and a whopping 2,050 lb-ft of torque from a 14.8-liter inline-six unit.

Turbochargers for natural gas engines are distinct from those used in diesel engines due to the unique demands of natural gas combustion like higher operating temperatures and distinct air-to-fuel ...

One other engine that competes with the Mack MP8 is the DD15 from Detroit Diesel engines, which also makes exactly 505 horsepower, but less torque, at 1,850 lb-ft. Mack, who recently made changes ...