2021 GMC Sierra Denali 2500HD/3500HD Fuel tank size
Depends on your version. Choose yours, or compare them here.
- 2500 Series and 3500 Series Standard Box (Except Double Cab Diesel) 36.0 gal
- 2500 Series and 3500 Series Standard Box (Double Cab Diesel) 29.4 gal
- 2500 Series and 3500 Series Long Box (Regular Cab Diesel) 28.0 gal
- 3500 Series Chassis Cab – Front Tank 23.5 gal·40.0 gal
- 3500 Series Chassis Cab – Rear Tank 23.5 gal·40.0 gal
36.0gal
2500 Series and 3500 Series Standard Box (Except Double Cab Diesel)
29.4gal
2500 Series and 3500 Series Standard Box (Double Cab Diesel)
28.0gal
2500 Series and 3500 Series Long Box (Regular Cab Diesel)
23.5gal
40.0gal
23.5gal
40.0gal
2021 GMC Sierra Denali 2500HD/3500HD Owner's Manual, PDF pages 405 and 406
136.3 L 36.0 galOpen the manual at this page ↗Added Oct 15, 2026
See where it's printed
Fuel tank size · 2500 Series and 3500 Series Standard Box (Except Double Cab Diesel) · PDF page 405
136.3 L 36.0 gal
Fuel tank size · 2500 Series and 3500 Series Standard Box (Double Cab Diesel) · PDF page 405
111.3 L 29.4 gal
Fuel tank size · 2500 Series and 3500 Series Long Box (Regular Cab Diesel) · PDF page 405
106.0 L 28.0 gal
Fuel tank size · 3500 Series Chassis Cab – Front Tank · PDF page 406
89.0 L 23.5 gal
Fuel tank size · 3500 Series Chassis Cab – Rear Tank · PDF page 406
151.4 L 40.0 gal
Fuel tank size · 3500 Series Chassis Cab – Front Tank · PDF page 406
89.0 L 23.5 gal
Fuel tank size · 3500 Series Chassis Cab – Rear Tank · PDF page 406
151.4 L 40.0 gal
2021 GMC Sierra Denali 2500HD/3500HD Owner's Manual, PDF page 405
136.3 L 36.0 galOpen the manual at this page ↗Added Oct 15, 2026
See where it's printed
Fuel tank size · 2500 Series and 3500 Series Standard Box (Except Double Cab Diesel) · PDF page 405
136.3 L 36.0 gal
2021 GMC Sierra Denali 2500HD/3500HD Owner's Manual, PDF page 405
111.3 L 29.4 galOpen the manual at this page ↗Added Oct 15, 2026
See where it's printed
Fuel tank size · 2500 Series and 3500 Series Standard Box (Double Cab Diesel) · PDF page 405
111.3 L 29.4 gal
2021 GMC Sierra Denali 2500HD/3500HD Owner's Manual, PDF page 405
106.0 L 28.0 galOpen the manual at this page ↗Added Oct 15, 2026
See where it's printed
Fuel tank size · 2500 Series and 3500 Series Long Box (Regular Cab Diesel) · PDF page 405
106.0 L 28.0 gal
2021 GMC Sierra Denali 2500HD/3500HD Owner's Manual, PDF page 406
89.0 L 23.5 galOpen the manual at this page ↗Added Oct 15, 2026
See where it's printed
Fuel tank size · 3500 Series Chassis Cab – Front Tank · PDF page 406
89.0 L 23.5 gal
Fuel tank size · 3500 Series Chassis Cab – Rear Tank · PDF page 406
151.4 L 40.0 gal
2021 GMC Sierra Denali 2500HD/3500HD Owner's Manual, PDF page 406
89.0 L 23.5 galOpen the manual at this page ↗Added Oct 15, 2026
See where it's printed
Fuel tank size · 3500 Series Chassis Cab – Front Tank · PDF page 406
89.0 L 23.5 gal
Fuel tank size · 3500 Series Chassis Cab – Rear Tank · PDF page 406
151.4 L 40.0 gal
All versions
| Applies to | Value | Manual says | Page |
|---|---|---|---|
| 2500 Series and 3500 Series Standard Box (Except Double Cab Diesel) | 36.0 gal | “136.3 L 36.0 gal” | PDF page 405 ↗ |
| 2500 Series and 3500 Series Standard Box (Double Cab Diesel) | 29.4 gal | “111.3 L 29.4 gal” | PDF page 405 ↗ |
| 2500 Series and 3500 Series Long Box (Regular Cab Diesel) | 28.0 gal | “106.0 L 28.0 gal” | PDF page 405 ↗ |
| 3500 Series Chassis Cab – Front Tank | 23.5 gal | “89.0 L 23.5 gal” | PDF page 406 ↗ |
| 3500 Series Chassis Cab – Rear Tank | 40.0 gal | “151.4 L 40.0 gal” | PDF page 406 ↗ |
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