The Ram 2500’s 5.7-liter HEMI V8 engine switches seamlessly from compressed natural gas (CNG) to gasoline when its alternative fuel is depleted. The truck travels 225 miles on CNG alone or a total of 745 miles when equipped with a 35-gal. reserve gasoline tank. With 429 ft.-lb. of torque, the 410-hp truck tows up to 17,970 lbs.