How many gallons of fuel does a 2020 Duramax hold?

The answer depends on which Duramax variant your 2020 GM pickup uses. In short, the light-duty 3.0L Duramax in the 1500 lineup uses a 24-gallon tank, while the heavy-duty 6.6L Duramax in the 2500HD/3500HD lineup uses a 36-gallon tank.

GM offered two Duramax diesel options in the 2020 lineup: a 3.0L inline-six for light-duty 1500 pickups, and a 6.6L V8 for heavy-duty 2500HD/3500HD trucks. The fuel-tank size matches the expected range and payload needs of each platform, with the lighter truck using a smaller tank and the heavier-duty model carrying more fuel to extend its range under load.

Duramax configurations and fuel-tank sizes

Below are the standard fuel-tank capacities by Duramax configuration for the 2020 model year.

• Light-duty 2020 Silverado/Sierra 1500 with 3.0L Duramax: 24 gallons


• Heavy-duty 2020 Silverado/Sierra HD 2500/3500 with 6.6L Duramax: 36 gallons

Note: These figures refer to the standard tank configurations. Variations by trim or optional equipment may occur; consult the owner's manual or dealer specifications for the exact figure on a given truck.

Summary

For the 2020 Duramax lineup, fuel capacity divides into two main figures: 24 gallons for the light-duty 1500s with the 3.0L Duramax, and 36 gallons for the heavy-duty 2500HD/3500HDs with the 6.6L Duramax. The tank size is aligned with the vehicle’s expected range and payload requirements.

How many gallons of diesel does a 6.6 Duramax hold?

The fuel tank capacity of a 6.6 Duramax truck, such as a 2500HD or 3500HD, typically ranges from 24 to 36 gallons, depending on the cab and bed configuration. Crew cab models generally have a 36-gallon tank. Extended cab and regular cab models may have slightly smaller tanks, typically around 24 to 26 gallons.

How many gallons does a 2020 Duramax hold?

The standard fuel tank capacity for a 2020 Duramax is typically 36 gallons for most Crew Cab and Double Cab Long Bed models, while Regular Cab models have a 28-gallon capacity. The Double Cab with a standard box is slightly smaller at 29.4 gallons.
 
You can watch this video to learn about the fuel economy of the 3.0L Duramax engine in the 2020 Chevy Silverado 1500: 1mUsed Car GuideYouTube · Apr 16, 2025

• 36 gallons: Crew Cab and Double Cab Long Bed models.
• 28 gallons: Regular Cab models.
• 29.4 gallons: Double Cab with a standard box. 

It's important to note that aftermarket tanks can be installed to increase capacity, such as 60 or 62-gallon options available for certain models, according to TITAN Fuel Tanks and S&B Filters.

How big is the fuel tank on a 2020 Duramax?

The stock tank is only 36 gallons.

How big is the fuel tank on a 6.6 Duramax?

A standard 6.6L Duramax fuel tank holds about 36 gallons, but replacement tanks are available with capacities of 52, 56, or 62 gallons. The specific capacity depends on the truck's model year, cab and bed configuration, and whether a standard or aftermarket tank is installed. For example, a 2020-2025 Crew Cab, Short Bed truck often has a stock 36-gallon tank, while aftermarket options can increase this to 56 or 62 gallons, as seen on Vin Specific Enterprises and TITAN Fuel Tanks. 

• Standard fuel tank: Approximately 36 gallons. 
• Aftermarket options:
  • 52 gallons: Available for older models (2001-2010). 
  • 56 gallons: Available for newer models (2020-2025). 
  • 62 gallons: Available for a wide range of models, often for Crew Cab Short Bed configurations.