19 MPG combined isn’t going to win any fuel-sipping awards, but for the 2024 GMC Sierra 4WD AT4X with the 3.0L Duramax diesel, it’s a reasonable compromise. This isn’t a truck bought for commuting; it’s a purpose-built machine for serious off-roading and confidently tackling challenging terrain. The AT4X buyer prioritizes capability, advanced suspension, and a rugged look over outright fuel efficiency, understanding that those attributes come with a cost at the pump.

City and highway performance

The EPA estimates 19 MPG in the city and 20 MPG on the highway for this specific configuration of the Sierra. Those numbers are surprisingly consistent, which shows the Duramax’s broad torque curve and the 10-speed automatic transmission’s ability to keep the engine in its sweet spot. Stop-and-go traffic will inevitably take a toll, the relatively small difference between city and highway figures suggests that even in urban environments, the diesel benefits from its inherent efficiency. Expect the highway number to drop significantly when towing or hauling heavy loads, activities this truck is designed to handle with ease.

Annual fuel cost

The EPA estimates an annual fuel cost of $2,950 for the 2024 GMC Sierra 4WD AT4X 3.0L Duramax. This figure is based on driving 15,000 miles per year, using a combination of city and highway driving (as reflected in the combined MPG figure), and assuming national average fuel prices. It’s important to remember that this is an estimate; your actual fuel costs will vary depending on your driving habits, local fuel prices, and the type of driving you do. If you primarily drive in the city or frequently tow, your annual fuel cost will likely be higher. If you primarily drive on the highway and practice efficient driving techniques, you might spend less. This number is a useful benchmark, but factor in your personal driving scenarios for a more accurate prediction.

Real-world expectations

Don’t expect to consistently achieve the EPA’s numbers if you’re regularly using the AT4X for its intended purpose. Climbing steep trails, navigating rocky terrain, and engaging four-wheel drive will all significantly decrease fuel economy. On longer highway trips without a load, it’s possible to meet or even slightly exceed the 20 MPG rating, especially if you maintain a steady speed and avoid aggressive acceleration. The key is to understand that this truck’s real-world fuel economy is heavily influenced by how and where it’s driven.

How it compares

Compared to other off-road-focused trucks, the Sierra AT4X with the Duramax holds its own. A comparable Ford F-150 Raptor typically achieves around 15 MPG combined with its EcoBoost V6, while offering more horsepower and a thrilling driving experience. The Ram 1500 TRX rarely exceeds 12 MPG with its supercharged V8. Even within the GMC Sierra lineup, opting for the 6.2L V8 in a standard 4WD trim will likely result in lower fuel economy than the 3.0L Duramax in the AT4X – browse all SIERRA MPG across all years. For those prioritizing fuel efficiency while still needing off-road capability, the Jeep Gladiator with its diesel engine comes closest, often achieving around 24 MPG combined in real-world driving. The Gladiator’s smaller size and lower towing capacity make it different than the full-size Sierra AT4X. The AT4X strikes a balance, offering respectable fuel economy within its class while delivering strong capability.

Tips to maximize efficiency

Take advantage of the Sierra’s drive modes. For everyday driving, select the mode that prioritizes fuel efficiency over performance. This will typically soften throttle response and optimize shift points for maximum MPG. When off-roading, prioritize the appropriate terrain mode for optimal traction and control, accepting the fuel economy penalty that comes with it.

Maintain consistent speed on the highway. The aerodynamic drag on a large truck like the Sierra increases dramatically at higher speeds. Using cruise control can help maintain a steady pace and avoid unnecessary acceleration, which burns extra fuel. Anticipate traffic flow and adjust your speed gradually to minimize braking and acceleration.

Keep your tires properly inflated. Underinflated tires increase rolling resistance, which reduces fuel economy. Check your tire pressure regularly and inflate them to the recommended pressure listed on the doorjamb or in the owner’s manual. Even a few PSI difference can impact fuel consumption, especially on a heavy vehicle like the AT4X.

Avoid unnecessary idling. Letting your engine idle for extended periods wastes fuel. If you’re stopped for more than a minute or two, turn off the engine. Modern engines start quickly and efficiently, so the fuel saved by turning it off outweighs the fuel used to restart it. This is more important than ever with today’s fuel prices.

Consider the weight you’re carrying. Hauling extra gear or equipment adds weight, which reduces fuel economy. Remove any unnecessary items from your truck bed or cabin to minimize the load on the engine. For more general information, take a look at all Gmc fuel economy data.