The 19 MPG combined is a real-world estimate for the 2021 GMC Sierra 4WD with the 2.7L turbocharged four-cylinder engine. This isn’t the most efficient full-size truck, but it’s reasonable given the Sierra’s capabilities and target buyer. This configuration suits those who need truck capabilities such as towing, hauling, and occasional off-road use, but not for constant heavy-duty work. They may accept slightly less gas mileage for the Sierra’s comfortable ride, spacious cabin, and respectable work abilities.

City and highway performance

The EPA estimates 18 MPG in the city and 21 MPG on the highway. These numbers show the disadvantage of a large, heavy truck in stop-and-go traffic. The Sierra’s weight and shape require more energy to accelerate in urban areas. On the highway, the 8-speed automatic transmission helps optimize engine speed at higher speeds, slightly improving fuel economy. Even then, the Sierra’s shape keeps it from being as efficient as a smaller vehicle.

Annual fuel cost

The EPA estimates the annual fuel cost for this Sierra configuration at $2,300. This is based on driving 15,000 miles per year and the national average fuel price at the time, which can change. This is a useful comparison point, but your actual expenses will depend on your driving and local fuel prices.

Real-world expectations

The EPA provides standardized data, but real-world fuel economy can differ. Driving habits, towing, heavy loads, and tire pressures can all change your MPG. Consider the 19 MPG combined rating a benchmark, possibly achievable in ideal conditions. In mixed driving, expect closer to 17-18 MPG. Consistent highway driving could get you over 21 MPG. Find more information on SIERRA MPG across all years on owner forums and fuel tracking apps.

How it compares

The 2021 Sierra 2.7L 4WD’s fuel economy is in the middle of its class. A comparable Ford F-150 with the 2.7L EcoBoost V6 and 4WD gets a slightly better 20 MPG combined. The Ram 1500 with the eTorque 3.6L V6 and 4WD is also around 20 MPG. A larger V8 in these trucks will typically mean significantly lower fuel economy, often in the 15-17 MPG range. The Toyota Tundra, often only available with a V8 that year, gets closer to 14 MPG combined. These are considerations for truck shoppers, trading MPG for capability.

Tips to maximize efficiency

Avoid hard acceleration. The 2.7L turbo engine uses more fuel when pushed. Accelerate slowly to allow the turbocharger to operate efficiently, saving fuel. Anticipate traffic and avoid sudden braking.

Keep tires properly inflated. Underinflated tires increase rolling resistance, making the engine work harder and use more fuel. Check your tire pressure and inflate to the levels on the door jamb sticker.

Reduce wind resistance. Removing unnecessary items from the truck bed, especially those that catch wind, can improve fuel economy on the highway. Use a tonneau cover to streamline airflow over the bed.

Don’t idle excessively. Idling wastes fuel, especially with a turbocharged engine. Turn off the engine when stopped for more than a minute or two. Modern engines restart quickly and efficiently, minimizing wear. For all Gmc fuel economy data, including trucks, see the EPA and manufacturer websites.