Based on data from 37 vehicles, 3,356 fuel-ups and 1,139,445 miles of driving, the 2021 GMC Sierra 3500 HD gets a combined Avg MPG of 13.86 with a 0.15 MPG margin of error.

Any Engine Type 6.6L V8 DIESEL (35) 6.6L V8 GAS (2) Any Body Style Crew Cab Pickup (10) Any Submodel SLE (2) SLT (3) AT4 (11) Denali (21)

Below you can see a distribution of the fuel-ups with 20 outliers (0.59%) removed.

Following shows the average MPG of each of the 37 vehicles in the system.

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• 2021 Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Feb 2021 • 51 Fuel-ups

  Property of Flatchevy

• 15.2 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2022 • 131 Fuel-ups

  Property of hamiltbl2

• 16.6 Avg MPG

• 2021 GMC Denali 3500HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Mar 2022 • 69 Fuel-ups

  Property of ob_1jr77

• 13.0 Avg MPG

• 2021 Duramax Denali 3500HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Sep 2024 • 3 Fuel-ups

  Property of Jeep4xeRubicon

• 89.1 Avg MPG

• Sully

  2021 GMC Sierra 3500 HD AT4 6.6L V8 GAS Automatic 6 Speed
  Added Sep 2021 • 73 Fuel-ups

  Property of kstile

• 12.9 Avg MPG

• Sierra 3500 HD

  2021 GMC Sierra 3500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 48 Fuel-ups

  Property of loricap

• 15.3 Avg MPG

• Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2021 • 198 Fuel-ups

  Property of rdf1982

• 12.3 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2023 • 221 Fuel-ups

  Property of jillandduane

• 12.6 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jan 2025 • 20 Fuel-ups

  Property of PedroMartinezJr

• 13.5 Avg MPG

• Sierra 3500 Dually

  2021 GMC Sierra 3500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2021 • 81 Fuel-ups

  Property of JoshMundy

• 12.1 Avg MPG

• GMC

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Mar 2024 • 32 Fuel-ups

  Property of bvermilion

• 13.0 Avg MPG

• Duramax

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 65 Fuel-ups

  Property of schroeder26

• 12.8 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 303 Fuel-ups

  Property of SeanAZ

• 14.3 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 201 Fuel-ups

  Property of Packert

• 13.4 Avg MPG

• AT4

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 143 Fuel-ups

  Property of jman3794

• 11.0 Avg MPG

• 2021 GMC Sierra 3500 HD AT4

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 166 Fuel-ups

  Property of wbernards

• 12.5 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2021 • 140 Fuel-ups

  Property of kmf620

• 15.7 Avg MPG

• AT4

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Mar 2021 • 281 Fuel-ups

  Property of cowdoc

• 18.6 Avg MPG

• Georgia

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Jan 2024 • 62 Fuel-ups

  Property of cniehaus

• 16.4 Avg MPG

• 2021 GMC AT4 3500

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Crew Cab Pickup
  Added Nov 2020 • 153 Fuel-ups

  Property of jr32313

• 14.8 Avg MPG

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