GMC was kind enough to lend TFL a brand new GMC Sierra HD All Terrain X with the 6.6L Duramax Turbo-diesel V8. As this is a diesel, we would expect the fuel economy to be better than that of a gasoline model. So, Roman decided to put this fuel economy to the test. From St. George, UT to our headquarters in Boulder, CO, the distance is 640 miles. Based on the size of the fuel tank in the Sierra HD, 36 gallons, this truck should be able to make it 640 miles on one tank, if it can average 18 MPG.
All Terrain X
However, this truck has the most beefy version of GMC’s off-road package. The All Terrain X package totals $2,990 on top of the $1,850 All Terrain package. What does all this cash get you? Black painted wheels, Goodyear Wrangler Duratrac tires, side steps and a sports bar with LED lights. Plus, all of the features of the Z71 off-road package. While this is great for going off-road, it will almost certainly take away from this Sierra’s fuel efficiency. While official fuel economy numbers for HD trucks are not available, due to the weight category of this truck, we were not entirely confident that the GMC could do it.
Results
The MPG results were not confidence boosting. Roman was only able to manage 12 MPG while cruising on the freeway at about 80 MPH. That, unfortunately, was not enough to make it to Boulder on one tank.
381 miles into the tank and 3/4 of those 36 gallons have been burnt away. However, the economy average was up to 15 MPG by this time. Furthermore, Roman had made it to Colorado.
By the time the fuel gauge read ’empty’ the average MPG was up to 15.4. Unfortunately, Roman had only made it so far as Eagle, CO, just outside of Vail. In total, the truck made it just over 500 miles on one tank. Not too shabby considering how capable it is off-road, and that it can tow 13,000 lbs.
