The 2021 GMC Sierra 2WD with the 3.0L Duramax diesel gets 26 MPG combined, which won’t win any green awards, but it offers a good balance of capability and efficiency that appeals to a specific truck buyer: the smart worker who values towing capacity and open-road comfort over outright payload or flashy off-road features. This Sierra configuration isn’t trying to be a Raptor-fighter or a dedicated work truck. It carves its own niche.

City and highway performance

The EPA estimates for the 2021 GMC Sierra 2WD 3.0L DuraMax are 23 MPG in the city and 30 MPG on the highway. This split highlights the engine’s strengths. The Duramax diesel’s torque-rich nature and the 10-speed automatic transmission enable relaxed cruising at highway speeds, contributing to its efficiency. Around town, where stop-and-go traffic strains any engine, the diesel still manages a respectable showing. While a gasoline-powered half-ton might get similar city mileage, the Sierra diesel’s effortless torque delivery makes it a more pleasant experience, especially when hauling or towing.

Annual fuel cost

According to the EPA, the annual fuel cost for the 2021 GMC Sierra 2WD 3.0L diesel is approximately $2,150. This figure is based on driving 15,000 miles per year and using national average fuel prices. It’s a useful benchmark, but remember your actual fuel costs will vary depending on your driving habits, local fuel prices, and how much you tow or haul. Understanding this EPA estimate helps you budget for your vehicle.

Real-world expectations

While the EPA figures provide a useful starting point, actual fuel economy often differs. Sierra 3.0L owners report achieving numbers close to the EPA estimates, especially on longer highway trips. However, factors such as aggressive driving, frequent towing, or extensive idling can significantly reduce fuel economy. Expect to see figures closer to the city estimate if your driving is primarily stop-and-go. Consistent highway driving, with minimal towing, might even push you slightly above the EPA’s 30 MPG estimate. Owners who carefully monitor their driving habits and use the Sierra’s driver-selectable modes can usually maximize their fuel efficiency.

How it compares

Compared to gasoline-powered half-ton trucks, the 2021 Sierra 3.0L diesel often delivers better fuel economy. For example, a 2021 Ford F-150 2WD with the 2.7L EcoBoost V6 is rated at 20 MPG combined, lagging the Sierra’s 26. The Ram 1500 eTorque V6, a mild hybrid, achieves 22 MPG combined. Where other manufacturers offer gasoline-powered mileage, GMC has a distinct advantage; all Gmc fuel economy data shows that GMC is committed to efficiency.

Even the previous-generation Sierra with a gasoline V8 struggles to match the diesel’s efficiency. The gasoline engines often offer more power and a different driving experience. The diesel prioritizes torque and fuel efficiency, designed for the priorities of the Sierra 3.0L diesel buyer. Take a look at SIERRA MPG across all years for a detailed view.

Tips to maximize efficiency

Smooth and steady acceleration is key to maximizing fuel economy in the 2021 Sierra 3.0L. Avoid aggressive starts and stops, as these actions consume excessive fuel. The Duramax diesel produces ample torque at low RPMs, so you don’t need to rev the engine to get moving. Anticipating traffic flow and maintaining a consistent speed will help increase MPG.

Tire pressure plays a surprisingly large role in fuel efficiency. Ensure your tires are properly inflated to the pressure recommended on the doorjamb sticker. Underinflated tires create more rolling resistance, which increases fuel consumption. Regularly check and adjust your tire pressure, especially during seasonal temperature changes, as temperature fluctuations can affect tire pressure.

Minimize unnecessary idling. Diesel engines, while efficient under load, consume a disproportionate amount of fuel when idling. If you anticipate being stopped for more than a minute, it’s generally more fuel-efficient to turn the engine off. Modern diesels are designed to be restarted without excessive wear, so don’t hesitate to use the stop-start feature if your Sierra is equipped with it.

Consider using the Sierra’s selectable drive modes. The “Normal” mode is generally optimized for everyday driving and fuel efficiency. However, if you’re consistently towing or hauling heavy loads, the “Tow/Haul” mode will adjust the transmission shift points to provide optimal power and reduce strain on the engine and transmission, though fuel economy will decrease.