2026 GMC Sierra 4WD AT4X: MPG and fuel economy
The 2026 GMC Sierra 4WD AT4X is rated by the U.S. Environmental Protection Agency at 19 combined MPG, with 19 MPG in the city and 20 MPG on the highway. That lands well below the average for cars in the Standard Pickup Trucks 4WD class in the same model year.
This page collects every fuel-economy figure the EPA publishes for the 2026 GMC Sierra 4WD AT4X. Below you will find the headline combined, city, and highway MPG, the estimated annual fuel cost at three different driving levels, the tailpipe CO₂ emissions, and a full breakdown of the engine and drivetrain. The EPA rates 2 separate variants of this car (different engine, transmission, or drivetrain combinations), and you can compare them side by side in the trims table. If you want to know whether this generation got more or less efficient over the years, the year-over-year table further down covers every model year the EPA has rated.
Key takeaways
- Returns 54% worse combined MPG than the average car in the Standard Pickup Trucks 4WD class for the 2026 model year (41.6 MPG class average).
- The most efficient car in the Standard Pickup Trucks 4WD class for the 2026 model year is the Rivian R1T Dual Max (22in) at 87 MPG.
- EPA estimates this car costs around $10,500 more in fuel over five years than an average new vehicle of the same model year.
Fuel economy at a glance
These are the EPA's official ratings for the 2026 GMC Sierra 4WD AT4X. The numbers come from a standardised laboratory test cycle and are the same figures that appear on the window sticker of every new car. Real-world mileage varies with driving style, weather, fuel quality, and how heavily loaded the car is.
When the EPA tests several variants of the same nameplate (for example, a front-wheel-drive version and an all-wheel-drive version), each gets its own rating. The figures shown here are the headline variant, taken as the configuration with the best combined MPG. The trims table further down covers all 2 variants side by side.
Combined MPG is a 55/45 weighted blend of the city and highway test cycles. The EPA uses it as the single number you can compare across the entire dataset, including hybrids and EVs (which use the equivalent MPGe figure).
| Combined MPG | 19 MPG |
| City MPG | 19 MPG |
| Highway MPG | 20 MPG |
| Annual fuel cost | $4,250 |
| Tailpipe CO₂ | 524 g/mi |
| Fuel type | Diesel |
How the 2026 GMC Sierra 4WD AT4X compares
The 2026 GMC Sierra 4WD AT4X returns 19 combined MPG. Cars in the Standard Pickup Trucks 4WD class for the same model year average 41.6 MPG, which puts this car behind the class average by about 54%.
The most efficient car in the Standard Pickup Trucks 4WD class for the 2026 model year is the Rivian R1T Dual Max (22in) at 87 MPG. The bar chart below puts the GMC Sierra 4WD AT4X alongside the class best and the class average so you can see the full picture.
For broader context, the average new car of the 2026 model year (across all classes) returns 45.5 MPG. Larger vehicles pull the all-cars average down, so do not use that figure on its own to judge a small car or a hybrid. The full list of the most efficient cars of the 2026 model year is on its own page.
Trim variants rated for 2026
The EPA rates 2 separate variants of the 2026 GMC Sierra 4WD AT4X. The differences come from the engine size, transmission type, and drivetrain (front-wheel drive, all-wheel drive, and so on). The same nameplate can land several MPG apart depending on the configuration you actually buy.
The most efficient configuration on this page returns 19 MPG, while the least efficient returns 15 MPG. That is a spread of 4 MPG between trims of the same nameplate.
| Engine and transmission | Drive | Combined | City | Highway | Annual cost |
|---|---|---|---|---|---|
| 3L, 6-cyl, turbo, Automatic 10-spd | 4-Wheel Drive | 19 MPG | 19 MPG | 20 MPG | $4,250 |
| 6.2L, 8-cyl, Automatic 10-spd | 4-Wheel Drive | 15 MPG | 14 MPG | 16 MPG | $4,600 |
Annual fuel cost across driving patterns
The headline annual fuel cost the EPA publishes assumes 15,000 miles of driving per year and a fuel mix of 55% city and 45% highway. The dollar figure is calculated using the EPA's current reference price for diesel, which is $5.40/gallon. EPA updates that reference periodically rather than tracking live pump prices, so treat it as a window-sticker estimate rather than today's pump number.
The table below scales the EPA's number to three common driving patterns. The combined MPG and the reference fuel price stay constant, only the annual mileage changes. To get a current-prices estimate, take your local gas price and multiply by 789.5 gallons (the car's annual consumption at the rated MPG).
| Driving pattern | Estimated annual fuel cost |
|---|---|
| Light driver, 7,500 miles per year | $2,125 |
| Average driver, 15,000 miles per year | $4,250 |
| Heavy driver, 25,000 miles per year | $7,083 |
Year-over-year MPG for the GMC Sierra 4WD AT4X
The EPA has rated the GMC Sierra 4WD AT4X across 4 model years, from 2023 GMC Sierra 4WD AT4X through 2026 GMC Sierra 4WD AT4X. The numbers below are the best combined MPG figure the EPA published for each year, which lets you see when the car was at its most efficient and how recent generations stack up.
Combined MPG has stayed in roughly the same range across the run. The peak rating came with the 2024 GMC Sierra 4WD AT4X at 19 MPG.
| Year | Combined MPG | Open year page |
|---|---|---|
| 2026 | 19 MPG | this page |
| 2025 | 19 MPG | 2025 GMC Sierra 4WD AT4X |
| 2024 | 19 MPG | 2024 GMC Sierra 4WD AT4X |
| 2023 | 15 MPG | 2023 GMC Sierra 4WD AT4X |
Compare against other Standard Pickup Trucks 4WD for 2026
If you are cross-shopping the 2026 GMC Sierra 4WD AT4X, the most useful comparison is against the other cars in the Standard Pickup Trucks 4WD class for the same model year. The list below shows the highest-MPG peers, ranked from most to least efficient. Click any of them to open its full page.
The Rivian R1T Dual Max (22in) leads this group at 87 MPG, 68 MPG ahead of the 2026 GMC Sierra 4WD AT4X.
Specifications
The 2026 GMC Sierra 4WD AT4X runs a 3-liter 6-cylinder turbocharged engine paired with a automatic 10-spd, sending power through 4-wheel drive.
Engine, transmission, and drivetrain together drive most of the variation in fuel economy across trims. A larger engine moves the car with less effort but burns more fuel. A turbo lets a small engine punch above its weight, often without much MPG penalty. All-wheel drive adds traction and weight, and usually costs a couple of MPG compared with two-wheel drive of the same engine.
- Vehicle class
- Standard Pickup Trucks 4WD
- Engine
- 3L 6-cylinder turbocharged
- Transmission
- Automatic 10-spd
- Drivetrain
- 4-Wheel Drive
- Fuel type
- Diesel
- Annual petroleum use
- 18.8 barrels per year
- Start-stop system
- Yes
Common questions about the 2026 GMC Sierra 4WD AT4X
Quick answers to the questions people most often search for when looking up the 2026 GMC Sierra 4WD AT4X.
-
Is the 2026 GMC Sierra 4WD AT4X fuel efficient?
Not particularly. The 2026 GMC Sierra 4WD AT4X returns 19 combined MPG, which trails the average car in the Standard Pickup Trucks 4WD class for the same model year by about 54%. -
What MPG does the 2026 GMC Sierra 4WD AT4X get?
The EPA rates the 2026 GMC Sierra 4WD AT4X at 19 combined MPG, 19 MPG in city driving, and 20 MPG on the highway. Real-world numbers depend on your driving style, the weather, and how loaded the car is. -
How much does it cost to fuel a 2026 GMC Sierra 4WD AT4X per year?
The EPA estimates an annual fuel cost of $4,250 for the 2026 GMC Sierra 4WD AT4X. That figure assumes 15,000 miles of driving per year, a 55% city and 45% highway split, and the EPA's published average fuel price for the rated fuel grade. -
What fuel does the 2026 GMC Sierra 4WD AT4X use?
The EPA lists the 2026 GMC Sierra 4WD AT4X as running on diesel. Using a different grade than the manufacturer specifies can affect fuel economy and engine longevity. -
Has the GMC Sierra 4WD AT4X become more fuel efficient over time?
Combined MPG has stayed close to flat across the run. Both the earliest (2023 GMC Sierra 4WD AT4X, 15 MPG) and most recent (2026 GMC Sierra 4WD AT4X, 19 MPG) versions sit in the same range. -
How much CO₂ does the 2026 GMC Sierra 4WD AT4X emit?
Tailpipe CO₂ emissions are 524 g/mi. Multiplied across a typical year of driving (15,000 miles) that works out to about 7,860 kilograms of CO₂. -
What is the difference between the city and highway MPG of the 2026 GMC Sierra 4WD AT4X?
City driving returns 19 MPG and highway driving returns 20 MPG, a gap of 1 MPG. The two figures are close enough that the car will hold its rated efficiency well across most driving patterns. -
What engine is in the 2026 GMC Sierra 4WD AT4X?
The 2026 GMC Sierra 4WD AT4X has a 3-liter 6-cylinder turbocharged engine. -
What transmission and drivetrain does the 2026 GMC Sierra 4WD AT4X have?
The 2026 GMC Sierra 4WD AT4X comes with a automatic 10-spd transmission and 4-wheel drive. -
How does the 2026 GMC Sierra 4WD AT4X compare to the best car in its class?
The most efficient car in the Standard Pickup Trucks 4WD class for the 2026 model year is the Rivian R1T Dual Max (22in) at 87 combined MPG. The GMC Sierra 4WD AT4X returns 19 MPG, a gap of 68 MPG. If you are comparing on fuel economy alone, the class leader is worth a look.
Source: U.S. EPA fuel economy dataset. Annual fuel cost figures assume 15,000 miles of driving per year and a 55% city, 45% highway split. Real-world mileage varies with driving conditions, vehicle maintenance, fuel quality, and driver behaviour.