17 MPG combined isn’t going to win any efficiency awards, but it’s the reality for the 2021 GMC Sierra 2WD with the 4.3L V6. This truck caters to someone needing a capable work truck without the frills, focused more on utility and upfront cost savings than using less gas. This Sierra configuration prioritizes a lower purchase price and adequate capability for basic tasks over outright fuel efficiency.

City and highway performance

The EPA estimates 16 MPG in the city and 21 MPG on the highway for this Sierra. The city figure reflects the stop-and-go nature of urban driving, where a larger displacement engine like the 4.3L V6 is less efficient due to frequent acceleration and idling. On the open road, at a steady cruising speed, the 21 MPG rating demonstrates the engine’s ability to achieve reasonable efficiency when it’s not under heavy load. The 6-speed automatic transmission, while simple by modern standards, helps optimize engine speed for both power and economy as best it can given its limitations.

Annual fuel cost

The EPA estimates that you’ll spend $2,600 per year on fuel with this particular 2021 GMC Sierra configuration. This figure is based on driving 15,000 miles per year, with 55% of those miles driven in the city and 45% on the highway. It also uses the national average fuel price at the time of calculation. While this provides a useful baseline, your actual fuel costs will vary depending on your driving habits, the type of driving you do, and fluctuations in fuel prices. For those who drive primarily on the highway, expect to spend less. If your daily grind involves heavy towing or constant city driving, that $2,600 figure is likely to be a low estimate.

Real-world expectations

While the EPA estimates provide a benchmark, real-world fuel economy often differs. Some Sierra owners report figures close to the EPA estimates, but achieving the rated 21 MPG on the highway requires a light foot and disciplined driving. Aggressive acceleration, heavy loads, or driving at speeds significantly above the speed limit will quickly diminish fuel economy. Owners using this truck primarily for short trips around town report numbers near the 16 MPG city figure, while those with longer commutes sometimes see better performance if driving style is closely monitored.

How it compares

The 2021 Sierra’s fuel economy lags behind some of its competitors, especially when they are equipped with smaller displacement and/or boosted engines. For example, the Ford F-150 with the 2.7L EcoBoost V6 is rated at 20 MPG combined, offering both more power and better fuel economy. Even a Ram 1500 with the eTorque mild-hybrid system can often surpass the Sierra’s V6 in real-world fuel economy. However, these more advanced powertrains typically come at a higher initial cost. Those willing to compromise on outright power and pay attention to driving habits may find the 2021 Chevrolet Colorado with its available 2.5L I4, rated at 22 MPG combined, a more fuel-efficient option, though it lacks the Sierra’s size and towing capacity. Potential buyers should carefully consider their needs and assess whether the savings in fuel outweigh the higher initial cost of other vehicles or potential sacrifices in capability. Consult all all Gmc fuel economy data when making a decision.

Tips to maximize efficiency

Gentle acceleration is key. The 4.3L V6 responds well to a light foot, so avoid aggressive starts and maintain a steady speed whenever possible. Building momentum gradually will significantly reduce fuel wasted during acceleration. Anticipate traffic flow to avoid unnecessary braking which further compounds inefficiency.

Maintain proper tire inflation. Underinflated tires increase rolling resistance, forcing the engine to work harder and burn more fuel. Check your tire pressure regularly and inflate them to the recommended pressure listed on the door jamb sticker. This is a simple step that can have a noticeable impact on fuel economy especially for a vehicle with a work duty pedigree.

Reduce unnecessary weight. The heavier the load, the more fuel the engine consumes to move it. Remove any unnecessary items from the cab and bed of the truck. Hauling around tools or materials that aren’t needed impacts your gas mileage. Consider the SIERRA MPG across all years with different bed setups for optimized weight.

Avoid idling. Excessive idling wastes fuel and produces emissions. If you’re stopped for more than a minute, turn off the engine. Modern vehicles are designed to restart quickly and efficiently, so there’s no need to let the engine run unnecessarily.

Use cruise control wisely. On long, flat stretches of highway, cruise control can help maintain a constant speed and optimize fuel economy. However, avoid using cruise control in hilly terrain, as the system may downshift frequently to maintain speed, which can actually decrease your fuel economy. Let the truck manage shifts in grade with your guidance for the most economical results.