Based on data from 71 vehicles, 4,523 fuel-ups and 1,457,483 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 (0.42%) 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 Apr 2023 • 111 Fuel-ups

  Property of bcfiremedic

• 11.9 Avg MPG

• 2021 Sierra Denali HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 208 Fuel-ups

  Property of LynnE24

• 14.2 Avg MPG

• 2021 GMC Sierra 2500 HD

  2021 GMC Sierra 2500 HD 6.6L V8 GAS Automatic 6 Speed
  Added Mar 2021 • 75 Fuel-ups

  Property of Hay_Man_40

• 11.4 Avg MPG

• 2021 Denali HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Nov 2020 • 102 Fuel-ups

  Property of DenaliDad

• 14.7 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLT 6.6L V8 GAS Automatic 6 Speed
  Added Jan 2021 • 251 Fuel-ups

  Property of kbeazley

• 10.7 Avg MPG

• Dads Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added Jan 2025 • 15 Fuel-ups

  Property of WillyM

• 12.0 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 6 Speed
  Added Jan 2025 • 10 Fuel-ups

  Property of keenwyatt

• 15.6 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Sep 2023 • 186 Fuel-ups

  Property of SeB21

• 17.1 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2024 • 35 Fuel-ups

  Property of crossfamily

• 16.3 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 GAS Automatic 6 Speed
  Added May 2021 • 256 Fuel-ups

  Property of Buellx72

• 11.3 Avg MPG

• Big Bubba. My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2021 • 114 Fuel-ups

  Property of moose57

• 16.5 Avg MPG

• GMC

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jul 2024 • 9 Fuel-ups

  Property of JK27

• 13.0 Avg MPG

• AT4 Whore

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2021 • 165 Fuel-ups

  Property of pigpen23

• 12.4 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLE 6.6L V8 GAS Automatic 6 Speed
  Added Nov 2024 • 19 Fuel-ups

  Property of Anticyclone

• 11.0 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD AT4 6.6L V8 GAS Automatic 6 Speed
  Added Jun 2021 • 200 Fuel-ups

  Property of gregnola

• 12.0 Avg MPG

• GMC AT4 - 21

  2021 GMC Sierra 2500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Sep 2024 • 6 Fuel-ups

  Property of Landmans

• 14.1 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD SLE 6.6L V8 GAS Automatic 10 Speed
  Added Oct 2021 • 169 Fuel-ups

  Property of bdamats

• 11.1 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2023 • 26 Fuel-ups

  Property of egobuster1

• 14.8 Avg MPG

• My Sierra 2500 HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jul 2024 • 32 Fuel-ups

  Property of josterhout1

• 15.4 Avg MPG

• 2021 Sierra 2500HD

  2021 GMC Sierra 2500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Jan 2024 • 61 Fuel-ups

  Property of Bost05

• 12.6 Avg MPG

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