15 MPG combined defines the 2025 GMC Sierra Mud Terrain Tires 4WD 6.2L 8-cyl. This isn’t a truck designed for the suburban school run or hypermiling exercises. It’s built for those who understand that an aggressive stance, massive off-road capability, and a potent V8 come with a fuel consumption penalty they are more than willing to accept. The buyer of this specific Sierra variant prioritizes raw power, an unmistakable presence, and the ability to conquer truly challenging terrain over anything resembling frugality. This is the truck for the serious off-roader, the rancher who needs to traverse undeveloped land, or the individual who simply demands the pinnacle of GMC truck performance and aesthetics, mud tires and all.

City and highway performance

Looking at the EPA estimates, the 14 MPG City figure for the 2025 Sierra Mud Terrain is entirely predictable. Hauling its substantial weight, spinning those aggressive, high-rolling-resistance tires from a standstill, and cycling through 10 gears in stop-and-go traffic puts a significant strain on the 6.2L V8. Expect much lower numbers if your daily commute involves heavy congestion or frequent short trips where the engine never fully warms up. On the highway, the 17 MPG rating provides a modest improvement. Here, the 10-speed automatic transmission works efficiently, allowing the big V8 to loaf at low RPMs. However, those knobby mud-terrain tires continue to exact their toll, creating more drag and rolling resistance than a standard all-season or even an all-terrain tire. Sustained speeds above 70 MPH, headwinds, or carrying heavy loads will see that 17 MPG number drop quickly.

Annual fuel cost

The EPA estimates an annual fuel cost of exactly $3,850 for the 2025 GMC Sierra Mud Terrain Tires 4WD 6.2L 8-cyl. This figure is calculated based on driving 15,000 miles per year, with an assumed mix of city and highway driving, and using national average fuel prices. For buyers of this particular Sierra, this isn’t a surprise; it’s an expected operational cost. They are not chasing the lowest running costs, but rather the ultimate capability and performance. Understanding that this annual expense is part of the package helps set realistic expectations. For a vehicle with its specific mission and powertrain combination, this budget should be factored into the overall cost of ownership, just like insurance and maintenance.

Real-world expectations

Real-world fuel economy for the 2025 Sierra Mud Terrain will likely hover around or even slightly below the EPA estimates for most owners. The very nature of this truck encourages behaviors that are not conducive to efficiency. Aggressive acceleration, frequent off-road excursions (where fuel consumption spikes dramatically), and hauling or towing heavy loads are common use cases. Those mud-terrain tires, while providing exceptional grip in challenging conditions, also contribute significantly to increased fuel consumption due to their weight, aggressive tread pattern, and higher rolling resistance compared to conventional street tires. Owners who regularly tap into the deep well of horsepower from the 6.2L V8 will find their city MPG closer to 12 or 13, and their highway figures perhaps in the low teens. The truck’s substantial weight and brick-like aerodynamics only compound the challenge. Expect to be a regular at the fuel pump.

How it compares

When directly comparing the 2025 Sierra Mud Terrain 6.2L to its closest rivals, it’s clear that efficiency is a secondary concern across the segment. The Ram 1500 Rebel with its 5.7L Hemi V8 and similar off-road tires, for instance, typically achieves around 17 MPG combined, with 15 City / 20 Highway, a slight edge, but still firmly in the “big truck V8” camp. The Ford F-150 Tremor with the 5.0L V8 can post similar numbers, often around 16 MPG combined (15 City / 18 Highway), but the Tremor can also be optioned with the 3.5L EcoBoost V6, which improves to around 18 MPG combined (16 City / 20 Highway), a more efficient alternative to the V8, for those willing to sacrifice some of that traditional V8 rumble. Even GMC’s own Sierra MPG across all years shows that moving to the 3.0L Duramax diesel engine in a similar configuration can elevate combined efficiency to around 24-26 MPG, an impressive jump. However, the buyer of the 6.2L Mud Terrain Sierra isn’t looking for a diesel’s torque curve or a turbo V6’s efficiency; they are buying the character and undeniable power of the naturally aspirated 6.2L V8, understanding its particular fuel thirst.

Tips to maximize efficiency

While the 2025 Sierra Mud Terrain isn’t an efficiency champion, there are still strategies to mitigate its fuel consumption. Maintaining proper tire pressure is important; those large mud-terrain tires can lose pressure quickly, and under-inflation significantly increases rolling resistance, making the engine work harder.

Adopting a smooth driving style will also pay dividends. Avoid aggressive acceleration and hard braking, which are particularly inefficient in a heavy vehicle. Gentle inputs on the throttle and anticipating traffic flow help the 10-speed transmission upshift sooner and avoid unnecessary kickdowns.

Minimizing unnecessary weight is another straightforward approach. Remove any heavy gear from the bed if it’s not needed for your current trip. Every extra pound the truck carries requires more fuel to move.

Aerodynamics are not the Sierra’s strong suit, especially with its factory lift and aggressive tires, but removing external accessories like roof racks or unsecured tonneau covers when not in use can slightly reduce drag and improve fuel economy, particularly at highway speeds.

Finally, consolidate trips whenever possible. The 6.2L V8 is least efficient when cold, and frequent short trips where the engine never reaches optimal operating temperature drastically reduce average MPG. Combining errands into a single longer journey can help improve overall efficiency.