2026 GMC Sierra 4WD with Sport Mode (3L 6-cyl) MPG & Specs
Quick answer
The 2026 GMC Sierra 4WD with Sport Mode gets an EPA-estimated 22/26 MPG (city/highway) and 24 MPG combined, with an estimated $3,300/year fuel cost and 428 g/mi CO₂. Engine: 3 L 6-cyl.
The 2026 GMC Sierra 4WD with Sport Mode with the 3-liter 6-cylinder diesel engine returns an EPA-estimated 22 MPG in the city and 26 MPG on the highway, for a combined 24 MPG. This page summarizes the official EPA fuel-economy and emissions data for this configuration.
| Engine | 3 L 6-cyl |
| Transmission | Automatic 10-spd |
| Drive | 4-Wheel Drive |
| Fuel type | Diesel |
| Vehicle class | Standard Pickup Trucks 4WD |
| MPG — city | 22 |
| MPG — highway | 26 |
| MPG — combined | 24 |
| Annual fuel cost* | $3,300 |
| CO₂ tailpipe | 428 g/mi |
| EPA GHG score | 4/10 |
How efficient is it?
With a combined 24 MPG, the 2026 GMC Sierra 4WD with Sport Mode sits in the moderate range for fuel economy. That is about 14% better than the typical Standard Pickup Trucks 4WD of its era (21 MPG class average), making it one of the more efficient choices in its class.
Fuel economy and running costs
At about $3,300 per year in fuel (EPA estimate, 15,000 mi/yr), fuel is a major part of the cost of owning the 2026 GMC Sierra 4WD with Sport Mode. Over five years that is roughly $16,500 at today's prices — before insurance, maintenance, and depreciation.
Emissions
The 2026 GMC Sierra 4WD with Sport Mode emits approximately 428 grams of CO₂ per mile at the tailpipe, earning an EPA greenhouse-gas score of 4 out of 10. Lower emissions generally track higher fuel economy.
How to read these numbers
EPA figures come from standardized laboratory test cycles and are the same estimates shown on the vehicle's window sticker. Your real-world mileage depends on driving style, conditions, fuel grade, and maintenance. Use combined MPG and annual fuel cost to compare vehicles fairly.