Can the all-new 2021 Chevy Suburban Duramax Diesel get over 30 miles per gallon in real-world driving conditions? That’s what we wanted to know so we gave it a try.

I spent a few hours driving a new Suburban with the 3.0L Duramax Diesel engine and 10-speed automatic transmission and tried to get the best fuel economy I could. Using the standard Driver Information Center (DIC) in the Suburban’s Gauge Cluster, I wanted to know if it was possible to break the 30 MPG barrier over a 50-mile stretch. After all, even 20 MPG a few years ago would be impressive. With the Duramax Diesel, could I best that by over 10 more miles per gallon? I set out to see.

2021 Chevy Suburban Duramax Diesel 30 MPG Challenge
Zane behind the wheel of the 2021 Chevy Suburban with the 3.0L Duramax Diesel

I drove on various surface roads in rural New Hampshire. Not flat, not straight, but also not too fast. Our loop included speeds of 35 to 65 miles per hour, with most of our time spent in the 40-50 miles per hour range.

I applied fuel-economy-saving techniques that I had learned from my decades of testing cars. Not too much throttle or brake, no cruise control, and staying in a light and fun mood during the process. Overall, my goal was to conserve momentum.  After that, it was all on the Suburban and its Duramax Diesel to give me good results.

And did it ever! Not only was I able to reach my 30 miles-per-gallon goal, but I actually did better. 32.8 MPG was the best figure I was able to squeak out in my 50-mile loop.

Could I have done better? With some practice, I actually think so! Was I happy with the results? Most definitely. Even a bit shocked!  The Chevrolet Suburban is one of the heaviest vehicles that GM makes (until the HUMMER EV rolls around, that is) and to get over 30 MPG is an amazing achievement of engineering.

With that sort of fuel economy, I would be able to drive from New Hampshire to Detroit, Michigan on a single tank of Diesel fuel.

LM2 Duramax 3.0L Turbo-Diesel I6 ENGINE SPECIFICATIONS

Engine type Dual Overhead Cams
Piston displacement, cu. in.(liter) 183 (3.00)
Bore and stroke, in.(cm.) 3.3 x 3.54 (8.38 x 8.99)
Compression ratio 15.0:1
Horsepower 277@3750 rpm
Kilowatts(kW) 206.64@3750 rpm
Torque (lb.-ft.) 460@1500 rpm
Newton – Meters (N-m) 621.00@1500 rpm


LM2 3.0L Duramax Diesel Horsepower and Torque Curves
LM2 3.0L Duramax Diesel Horsepower and Torque Curves