In terms of fuel economy, the winner hands-down is the 3.0L turbo-diesel Duramax, with up to 29 mpg highway in the Silverado 1500. According to Fuelly, a 6.6L turbo-diesel Duramax-equipped Sierra ...

Feeding this system is a 5.8-gallon urea tank that is expected to last for an entire oil-change interval, but if the truck is used for extremely heavy towing it may be expended earlier.

A new, 36-gallon (136 L) fuel tank is standard on all models and, with the improved fuel efficiency of the powertrains, enables a cruising range of up about 680 miles (1,090 km) with the Duramax 6.6L.