Based on data from 36 vehicles, 2,706 fuel-ups and 907,702 miles of driving, the 2021 GMC Sierra 3500 HD gets a combined Avg MPG of 13.84 with a 0.16 MPG margin of error.

Any Engine Type 6.6L V8 DIESEL (34) 6.6L V8 GAS (2) Any Body Style Crew Cab Pickup (11) Any Submodel SLE (2) SLT (3) AT4 (11) Denali (20)

Below you can see a distribution of the fuel-ups with 12 outliers (0.44%) removed.

Following shows the average MPG of each of the 36 vehicles in the system.

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• AT4

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Mar 2021 • 215 Fuel-ups

  Property of cowdoc

• 18.7 Avg MPG

• Adrian

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Aug 2022 • 128 Fuel-ups

  Property of stu1029

• 15.9 Avg MPG

• Thor

  2021 GMC Sierra 3500 HD SLE 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Nov 2021 • 143 Fuel-ups

  Property of jdnewman2021

• 11.9 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 101 Fuel-ups

  Property of ivandude44

• 14.3 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 144 Fuel-ups

  Property of Packert

• 13.2 Avg MPG

• GMC

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Mar 2024 • 5 Fuel-ups

  Property of bvermilion

• 12.9 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 228 Fuel-ups

  Property of SeanAZ

• 13.7 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2021 • 106 Fuel-ups

  Property of kmf620

• 15.4 Avg MPG

• Georgia

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Jan 2024 • 17 Fuel-ups

  Property of cniehaus

• 16.8 Avg MPG

• Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2021 • 151 Fuel-ups

  Property of rdf1982

• 12.1 Avg MPG

• Sierra 3500 HD

  2021 GMC Sierra 3500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 33 Fuel-ups

  Property of loricap

• 14.3 Avg MPG

• AT4

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Jun 2021 • 82 Fuel-ups

  Property of crossmanj21

• 14.7 Avg MPG

• Sierra 3500 Dually

  2021 GMC Sierra 3500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2021 • 69 Fuel-ups

  Property of JoshMundy

• 11.8 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2022 • 87 Fuel-ups

  Property of hamiltbl2

• 15.8 Avg MPG

• 2021 GMC AT4 3500

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Crew Cab Pickup
  Added Nov 2020 • 130 Fuel-ups

  Property of jr32313

• 14.7 Avg MPG

• 2021 Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Feb 2021 • 34 Fuel-ups

  Property of Flatchevy

• 15.8 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jun 2023 • 156 Fuel-ups

  Property of jillandduane

• 12.4 Avg MPG

• GMC Sierra 3500 HD AT4

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 111 Fuel-ups

  Property of wbernards

• 13.2 Avg MPG

• Sully

  2021 GMC Sierra 3500 HD AT4 6.6L V8 GAS Automatic 6 Speed
  Added Sep 2021 • 57 Fuel-ups

  Property of kstile

• 12.8 Avg MPG

• 2021 GMC Sierra 3500 HD Denali

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Mar 2022 • 105 Fuel-ups

  Property of windycitypilot

• 16.0 Avg MPG

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