24 MPG combined might not sound like a monumental achievement in 2024, but it’s genuinely impressive coming from the 2020 GMC Sierra 4WD with the 3.0L Duramax diesel. This isn’t a compact crossover; it’s a full-size pickup truck, designed to haul, tow, and tackle tough terrain. The fact that it can achieve mileage figures rivaling some mid-size SUVs shows good engineering.

City and highway performance

The EPA estimates for the 2020 GMC Sierra 4WD 3.0L diesel are 22 MPG in the city and 26 MPG on the highway. These numbers reflect the characteristics of the Duramax engine and the smart 10-speed automatic transmission. The broad torque curve of the diesel means less downshifting and easier acceleration around town, contributing to the respectable city mileage. On the highway, the transmission’s multiple gears allow the engine to settle into a fuel-sipping cruise. Of course, these figures are laboratory tests. Individual results are highly dependent on driving style, load, and terrain.

Annual fuel cost

The EPA calculates the annual fuel cost for the 2020 GMC Sierra 4WD 3.0L diesel to be $2,300. This estimate is based on driving 15,000 miles per year, using a blend of city and highway driving, and factoring in national average fuel prices. It’s a useful benchmark for comparison, but keep in mind that your actual costs can vary significantly based on where you live (fuel prices fluctuate widely) and how you drive. It also assumes the user is using the correct type and grade of fuel.

Real-world expectations

The key to understanding the fuel economy of this Sierra lies in appreciating its intended use. This truck appeals to buyers who need genuine capability, whether for work or recreation. They’re often towing boats or trailers, hauling equipment, or navigating challenging conditions where all-wheel drive is essential. These activities will, of course, decrease fuel economy. However, when unladen and driven conservatively, many owners report fuel economy figures that meet or even exceed the EPA estimates, especially on long highway trips. The diesel’s efficiency shines on long hauls, making it a smart choice for those who rack up significant mileage.

How it compares

Compared to its gasoline-powered counterparts, the 3.0L diesel shines. For example, the 2020 Sierra 4WD with the 5.3L V8 is EPA-rated at 17 MPG combined. That’s a significant drop. Even Ford’s F-150 with the 2.7L EcoBoost typically hovers around 20 MPG in real-world driving for a 4×4 model. The RAM 1500 EcoDiesel, a direct competitor, achieves similar EPA ratings to the Sierra, but some owners might find advantages or disadvantages in ride quality or fuel efficiency across brands. Before making a decision, it´s always beneficial to compare SIERRA MPG across all years. For buyers prioritizing fuel economy in a full-size truck, the diesel is a good option, but for those who don’t need the diesel’s torque, other options on all GMC vehicles can be compared by examining all Gmc fuel economy data.

Tips to maximize efficiency

The 3.0L Duramax responds well to a smooth, steady driving style. Avoid aggressive acceleration and hard braking, as these habits will quickly deplete your fuel tank. The engine’s ample torque allows you to maintain speed without excessive throttle input, leading to improved economy.

Regular maintenance is critical for optimal fuel efficiency. Ensure your tires are properly inflated, and follow the recommended service schedule for oil changes and filter replacements. A well-maintained engine runs more efficiently and burns fuel more cleanly.

Minimize idling. Diesel engines, in particular, consume a surprising amount of fuel when idling for extended periods. If you’re stopped for more than a minute or two, it’s generally more efficient to turn off the engine.

Consider removing unnecessary weight from the truck bed. Every pound counts when it comes to fuel economy. Clearing out tools, equipment, or other items you don’t need on a regular basis can make a noticeable difference, especially around town.