Based on data from 74 vehicles, 4,825 fuel-ups and 1,559,633 miles of driving, the 2021 GMC Sierra 2500 HD gets a combined Avg MPG of 13.18 with a 0.11 MPG margin of error.

Any Engine Type 6.6L V8 DIESEL (56) 6.6L V8 GAS (17) Any Body Style Extended Cab Pickup (1) Crew Cab Pickup (16) Any Submodel Base (3) SLE (7) SLT (10) AT4 (24) Denali (30)

Below you can see a distribution of the fuel-ups with 19 outliers (0.39%) removed.

Following shows the average MPG of each of the 74 vehicles in the system.

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• 2021 Sierra 2500HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Jan 2024 • 78 Fuel-ups

  Property of Bost05

• 12.6 Avg MPG

• GMC

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jul 2024 • 26 Fuel-ups

  Property of JK27

• 12.7 Avg MPG

• AT4

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Oct 2022 • 91 Fuel-ups

  Property of scrabble890

• 14.3 Avg MPG

• AT4 Whore

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2021 • 176 Fuel-ups

  Property of pigpen23

• 12.4 Avg MPG

• GMC Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Apr 2023 • 45 Fuel-ups

  Property of Jdcompman

• 15.9 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLE 6.6L V8 GAS Automatic 10 Speed
  Added Oct 2021 • 182 Fuel-ups

  Property of bdamats

• 11.1 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLE 6.6L V8 DIESEL Automatic 6 Speed
  Added Apr 2023 • 273 Fuel-ups

  Property of mcgr0401

• 13.1 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 GAS Automatic 6 Speed
  Added May 2021 • 272 Fuel-ups

  Property of Buellx72

• 11.3 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD 6.6L V8 DIESEL Automatic 10 Speed
  Added Apr 2025 • 21 Fuel-ups

  Property of subie-doo

• 12.9 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLT 6.6L V8 GAS Automatic 6 Speed
  Added Jan 2021 • 42 Fuel-ups

  Property of NGreen08

• 10.3 Avg MPG

• Dads Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added Jan 2025 • 34 Fuel-ups

  Property of WillyM

• 12.7 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Sep 2023 • 200 Fuel-ups

  Property of SeB21

• 17.1 Avg MPG

• 2021 Denali HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Nov 2020 • 109 Fuel-ups

  Property of DenaliDad

• 14.8 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jul 2024 • 39 Fuel-ups

  Property of josterhout1

• 15.6 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Apr 2023 • 129 Fuel-ups

  Property of bcfiremedic

• 11.9 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2021 • 159 Fuel-ups

  Property of xETERNALx

• 13.6 Avg MPG

• 2021

  2021 GMC Sierra 2500 HD Denali Crew Cab Pickup
  Added Dec 2020 • 212 Fuel-ups

  Property of lampmant

• 13.0 Avg MPG

• Truck

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Nov 2024 • 19 Fuel-ups

  Property of MontanaRaptor

• 15.5 Avg MPG

• BigTruck

  2021 GMC Sierra 2500 HD 6.6L V8 GAS Automatic 6 Speed Crew Cab Pickup
  Added Mar 2023 • 68 Fuel-ups

  Property of pmhanson

• 13.1 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2023 • 30 Fuel-ups

  Property of egobuster1

• 14.6 Avg MPG

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