How many miles per gallon does a 2021 Silverado 3500 HD diesel get?

Typically, the 2021 Silverado 3500 HD equipped with the 6.6L Duramax turbo-diesel and an Allison 10-speed automatic averages around 18 miles per gallon (mpg) in combined driving. Two-wheel drive models tend to be a notch more fuel-efficient than their four-wheel drive counterparts, with real-world results varying based on payload, terrain, and driving style.

Official estimates and what they mean

EPA ratings provide a baseline for comparison across configurations. The following ranges reflect common 2021 Duramax diesel versions of the Silverado 3500 HD, noting that numbers vary with cab/bed combinations and axle setups.

• 2WD Duramax Diesel: City about 15 mpg; Highway about 23 mpg; Combined around 18–19 mpg.


• 4x4 Duramax Diesel: City about 14–15 mpg; Highway about 21–22 mpg; Combined around 17–18 mpg.

Keep in mind that real-world mileage can differ from these figures due to towing, payload, topography, and driving habits.

What factors influence MPG in daily use

Several variables can shift fuel economy away from the EPA baselines. Understanding these can help set expectations and optimize performance on the job or daily driving:

• Payload and towing weight


• Drivetrain configuration (2WD vs. 4x4) and axle ratio


• Tire size, tread, and inflation pressure


• Driving style, including acceleration, speed, and idling time


• Terrain and road grade (hills, mountains, and city stop-and-go)


• Vehicle condition and maintenance (air filters, engine tune, and exhaust system)

In practice, a Silverado 3500 HD diesel used primarily for light duty and highway driving will approach the upper end of these ranges, while heavy towing, high payload, or frequent starts and climbs can pull mpg down significantly.

Practical tips to maximize mpg

Even within the same model year, small changes can yield noticeable gains. Maintain proper tire pressure, remove unnecessary weight, use cruise control on highways when appropriate, and plan routes to minimize braking and idle time. Regular maintenance, including air filters and oil changes, also helps sustain efficiency.

Summary

The 2021 Silverado 3500 HD diesel delivers solid highway efficiency for a heavy-duty pickup, with typical combined mpg in the high teens. Expect roughly 18–19 mpg combined for 2WD and about 17–18 mpg combined for 4x4 configurations, with real-world results influenced by payload, towing, and driving conditions. If MPG is a priority, plan for lighter payload, highway driving, and careful maintenance to approach the upper end of the EPA estimates.

How many miles per gallon does a 2021 Chevy Silverado 2500HD diesel get?

The 2021 Silverado 2500 diesel doesn't have an official EPA rating, but real-world tests show it gets around 16-18 mpg combined, with highway driving typically achieving 17-20 mpg and city driving being closer to 15-17 mpg. The actual mileage depends heavily on driving style, terrain, and whether the truck is being used for towing or hauling. 
You can watch this video to see a real-world MPG test of a 2021 Silverado 2500 HD Duramax: 41sMyks GarageYouTube · Dec 21, 2021

• Combined driving: Expect around 16-18 mpg based on a mix of highway and city conditions. 
• Highway driving: You can likely achieve 17-20 mpg at speeds of around 70 mph, as seen in real-world tests. 
• City driving: Real-world city mileage is generally lower, around 15-17 mpg. 
• Towing and hauling: Fuel economy will be significantly lower when towing heavy loads. 

This video demonstrates the fuel economy difference between driving at 55 and 70 mph: 1mPickup Truck Plus SUV TalkYouTube · Apr 3, 2021

How many miles per gallon does a 3500 diesel get?

Efficiency leaders: Chevrolet/GMC 2500/3500 Duramax 6.6L, Ford F-250/F-350 6.7L, Ram 2500/3500 6.7L. Unloaded highway runs often deliver 17–20 mpg when geared sensibly.

What fuel mileage does a 6.6 l Duramax diesel get?

The 6.6L Duramax engine's MPG varies, but typically ranges from 15-18 MPG for mixed driving and 17-20 MPG for unloaded highway driving. Actual mileage depends heavily on factors like driving conditions, towing, and the specific model year. Some newer models achieve higher efficiency, with a 2025 Silverado HD hitting 20.4 MPG on a controlled highway loop. 
This video shows a fuel economy test of a 2021 Chevy Silverado HD with the 6.6L Duramax engine towing a trailer: 48struckguyjoeYouTube · Jan 15, 2021
Mileage breakdown by driving type: 
This video demonstrates a fuel economy test of a 2024 Chevy Silverado HD Duramax: 57sDaily MotorYouTube · Jun 27, 2023

• Mixed/City: Around 15 MPG or lower, especially with stop-and-go traffic. 
• Highway (unloaded): Typically 17-20 MPG, but can vary with speed. 
• Towing: Expect significantly lower mileage, often in the 10-14 MPG range depending on the load and terrain. 

Factors that influence MPG:

• Towing and load: Hauling heavy loads reduces fuel efficiency. 
• Driving conditions: Hilly terrain or stop-and-go city traffic lowers MPG. 
• Vehicle age and break-in: Newer trucks may improve after an initial break-in period, with some owners reporting increased mileage after a few thousand miles. 
• Other factors: Speed, road conditions, and factors like the truck's emissions system (e.g., temporary DPF regen cycles) can also have an effect. 

You can watch this video to see real-world mileage results for a 2022 GMC Sierra 2500 Duramax: 1mDaily MotorYouTube · Mar 26, 2022

How do you get 30 MPG on a Duramax?

General Tips for Better MPG

1. Don't let your truck idle for long periods of time if you can help it. Idling burns a lot of fuel and your gas mileage will take a hit.
2. Don't be heavy on the gas.
3. Watch your tire pressure.
4. Service and maintain your Duramax truck regularly.