Based on data from 37 vehicles, 3,243 fuel-ups and 1,099,699 miles of driving, the 2021 GMC Sierra 3500 HD gets a combined Avg MPG of 13.89 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 (11) Any Submodel SLE (2) SLT (3) AT4 (11) Denali (21)

Below you can see a distribution of the fuel-ups with 16 outliers (0.49%) removed.

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

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• Sierra 3500 HD

  2021 GMC Sierra 3500 HD SLT 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 44 Fuel-ups

  Property of loricap

• 15.0 Avg MPG

• AT4

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Jun 2021 • 95 Fuel-ups

  Property of crossmanj21

• 14.8 Avg MPG

• GMC Diesel

  2021 GMC Sierra 3500 HD SLE 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Apr 2021 • 94 Fuel-ups

  Property of rspeters

• 13.0 Avg MPG

• Denali 3500

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Dec 2020 • 170 Fuel-ups

  Property of caddydaddy7

• 14.7 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 • 109 Fuel-ups

  Property of windycitypilot

• 16.0 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jul 2021 • 57 Fuel-ups

  Property of rzrscubasteve03

• 13.4 Avg MPG

• Odin

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Mar 2022 • 31 Fuel-ups

  Property of en3chix

• 11.2 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD AT4 6.6L V8 DIESEL Automatic 10 Speed
  Added Apr 2021 • 36 Fuel-ups

  Property of JBAero

• 11.1 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Nov 2024 • 19 Fuel-ups

  Property of kdreverman

• 13.9 Avg MPG

• Frosty

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Jul 2021 • 8 Fuel-ups

  Property of iammrniceguy

• 9.3 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD SLT 6.6L V8 GAS Automatic 6 Speed
  Added Jun 2021 • 58 Fuel-ups

  Property of gmc3500

• 13.0 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Apr 2021 • 66 Fuel-ups

  Property of michael1538

• 10.7 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 Jan 2021 • 34 Fuel-ups

  Property of windycitypilot

• 14.5 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Sep 2021 • 13 Fuel-ups

  Property of jjchambs

• 13.4 Avg MPG

• Bob's Denali

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed Crew Cab Pickup
  Added Jun 2022 • 27 Fuel-ups

  Property of Pierce56

• 10.6 Avg MPG

• 2021 Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added May 2021 • 21 Fuel-ups

  Property of joshuaw

• 11.5 Avg MPG

• My Sierra 3500 HD

  2021 GMC Sierra 3500 HD Denali 6.6L V8 DIESEL Automatic 10 Speed
  Added Apr 2021 • 26 Fuel-ups

  Property of Benilac20

• 13.0 Avg MPG

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