Based on data from 71 vehicles, 4,585 fuel-ups and 1,478,354 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 (53) 6.6L V8 GAS (17) Any Body Style Extended Cab Pickup (1) Crew Cab Pickup (16) Any Submodel Base (2) SLE (7) SLT (10) AT4 (23) Denali (29)

Below you can see a distribution of the fuel-ups with 19 outliers (0.41%) removed.

Following shows the average MPG of each of the 71 vehicles in the system.

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• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 113 Fuel-ups

  Property of mbrent77

• 15.7 Avg MPG

• 2500Hd GMC

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added May 2021 • 154 Fuel-ups

  Property of jmgolden1978

• 14.0 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLE 6.6L V8 DIESEL Automatic 6 Speed
  Added Apr 2023 • 253 Fuel-ups

  Property of mcgr0401

• 13.1 Avg MPG

• Dads Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added Jan 2025 • 20 Fuel-ups

  Property of WillyM

• 12.2 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 GAS Automatic 6 Speed
  Added May 2021 • 259 Fuel-ups

  Property of Buellx72

• 11.3 Avg MPG

• 2021

  2021 GMC Sierra 2500 HD Denali Crew Cab Pickup
  Added Dec 2020 • 206 Fuel-ups

  Property of lampmant

• 13.0 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added Jul 2024 • 17 Fuel-ups

  Property of jbhardman

• 13.2 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Apr 2023 • 114 Fuel-ups

  Property of bcfiremedic

• 11.9 Avg MPG

• GMC

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jul 2024 • 16 Fuel-ups

  Property of JK27

• 13.1 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLE 6.6L V8 GAS Automatic 6 Speed
  Added Nov 2024 • 21 Fuel-ups

  Property of Anticyclone

• 11.3 Avg MPG

• 2021 Denali HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Nov 2020 • 103 Fuel-ups

  Property of DenaliDad

• 14.7 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Sep 2023 • 189 Fuel-ups

  Property of SeB21

• 17.1 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2023 • 27 Fuel-ups

  Property of egobuster1

• 14.7 Avg MPG

• AT4

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Oct 2022 • 86 Fuel-ups

  Property of scrabble890

• 14.3 Avg MPG

• 2021 Sierra Denali HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 213 Fuel-ups

  Property of LynnE24

• 14.2 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 6 Speed
  Added Jan 2025 • 12 Fuel-ups

  Property of keenwyatt

• 14.5 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLT 6.6L V8 GAS Automatic 6 Speed
  Added Jan 2021 • 252 Fuel-ups

  Property of kbeazley

• 10.7 Avg MPG

• 2021 Sierra 2500HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Jan 2024 • 70 Fuel-ups

  Property of Bost05

• 12.5 Avg MPG

• Sierra 2500 HD aka Sully

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 125 Fuel-ups

  Property of Ryot

• 12.0 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLE 6.6L V8 GAS Automatic 10 Speed
  Added Oct 2021 • 171 Fuel-ups

  Property of bdamats

• 11.2 Avg MPG

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