2026 · Full-Size Pickup · Diesel

2026 GMC Sierra Diesel MPG & fuel economy

The 2026 GMC Sierra Diesel is a full-size pickup offered in 4 EPA-rated configurations. The most efficient version returns 25 MPG combined (23 city / 28 highway) on diesel. Across the lineup, combined ratings range from 19 to 25 MPG. That's down 1 MPG from the 2025 model. Among 21 full-size pickups rated for 2026, it ranks 15th for lowest fuel cost. At 15,000 miles a year with $3.70/gal diesel fuel, it costs about $2,220 a year to fuel.

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Combined 25 MPG 23 MPG city · 28 MPG hwy

Driving range — not published for this model

Your fuel cost $2,220 15,000 mi/yr · $14.80 per 100 mi

Class rank, 2026 #15 of 21 Full-Size Pickups by fuel cost

What will it cost you?

Your mileage and prices are saved and used across the site.

Miles per year Diesel $/gal

Fuel average

The 2026 GMC Sierra Diesel's fuel average is 10.6 km/L (9.4 L/100 km), or 25 MPG combined: 9.8 km/L in the city and 11.9 km/L on the highway.

	MPG	km/L	L/100 km
City	23	9.8	10.2
Highway	28	11.9	8.4
Combined	25	10.6	9.4

How it ranks among 2026 Full-Size Pickups

Full class ranking →

1Rivian R1T87 MPGe $1,048
2Tesla Cybertruck79 MPGe $1,158
3Chevrolet Silverado EV70 MPGe $1,291
4GMC Sierra EV68 MPGe $1,336
5Ford F150 Hybrid24 MPG $1,938
···
15GMC Sierra Diesel25 MPG $2,220
···
21Jeep Gladiator19 MPG $2,447

2026 Sierra DieselOther full-size pickupsClass median: $2,214/yr

Annual fuel cost at 15,000 miles and default prices; shorter bars cost less.

Sierra Diesel MPG across model years

Full history →

4 EPA-rated configurations

Configuration	Type	City	Hwy	Combined	Range	Your cost / yr
RWD · 3.0L 6-cyl turbo · 10-speed automatic Sierra 2WD	Diesel	23 MPG	28 MPG	25 MPG	—	$2,220
4WD · 3.0L 6-cyl turbo · 10-speed automatic Sierra 4WD with Sport Mode	Diesel	22 MPG	26 MPG	24 MPG	—	$2,312
4WD · 3.0L 6-cyl turbo · 10-speed automatic Sierra Mud Terrain Tires with Sport Mode	Diesel	21 MPG	24 MPG	23 MPG	—	$2,413
4WD · 3.0L 6-cyl turbo · 10-speed automatic Sierra 4WD AT4X with Sport Mode	Diesel	19 MPG	20 MPG	19 MPG	—	$2,921

Specs (most efficient configuration)

Fuel: Diesel
Engine / motor: 3.0L 6-cyl turbo
Transmission: 10-speed automatic
Drivetrain: RWD
Tailpipe CO₂: 402 g/mi
EPA fuel economy score: 5/10
EPA greenhouse gas score: 4/10

2026 GMC Sierra Diesel vs. rivals

vs Chevrolet Silverado Diesel 25 MPG · $2,220/yr Same fuel cost vs Ford F150 21 MPG · $2,214/yr F150 saves $6/yr vs Nissan Frontier 21 MPG · $2,214/yr Frontier saves $6/yr vs Chevrolet Colorado 21 MPG · $2,214/yr Colorado saves $6/yr vs Honda Ridgeline 21 MPG · $2,214/yr Ridgeline saves $6/yr vs Ram 1500 21 MPG · $2,214/yr 1500 saves $6/yr vs Chevrolet Silverado 20 MPG · $2,325/yr Sierra Diesel saves $105/yr vs Toyota Tundra 20 MPG · $2,325/yr Sierra Diesel saves $105/yr vs Jeep Gladiator 19 MPG · $2,447/yr Sierra Diesel saves $227/yr vs GMC Sierra 20 MPG · $2,325/yr Sierra Diesel saves $105/yr vs GMC Sierra EV 68 MPGe · $1,336/yr Sierra EV saves $884/yr

Compare the 2026 Sierra Diesel

With any other car from any year, including other Sierra Diesel model years. Type a year to jump, e.g. "2015 Accord".

Same year, other powertrains: 2026 GMC Sierra (20 MPG), 2026 GMC Sierra EV (68 MPGe)

Frequently asked questions

What is the gas mileage of the 2026 GMC Sierra Diesel?

Up to 25 MPG combined (23 city / 28 highway); ratings range from 19 to 25 MPG depending on configuration.

What fuel does the 2026 GMC Sierra Diesel use?

Diesel.

What is the fuel average in km/L for the 2026 GMC Sierra Diesel?