Chevy Suburban Diesel Highway Fuel Economy Tested: Video29
GM Authority recently spent some time with the 2023 Chevy Suburban motivated by the optional 3.0L I6 LM2 turbodiesel Duramax engine. We also asked you what you most want to know about our experiences with the full-size SUV.
The most common question by far from GM Authority readers about our Suburban diesel tester was about the highway fuel economy. So, we took it out to discover how efficiency it is on the open road. The video below – hosted by GM Authority Executive Editor, Alex Luft – shows the test and results first hand.
We chose a 15-mile stretch of highway to test our 2023 Chevy Suburban diesel. The tests were performed in South Florida in temperatures of 70-80 degrees Fahrenheit at 70 mph on cruise control to ensure consistent speed. We tested the SUV three times to eliminate any possible outliers.
On the first attempt, we drove our 2023 Chevy Suburban diesel 15.4 miles at an average speed of 69.8 mph. Fuel economy averaged out to 32.8 miles per gallon. These results are on the high side, likely due to strong tailwinds during the test drive.
During the second test, we drove the Suburban diesel SUV for a distance of 15.2 miles. Speed was an average of 68.5 mph, and fuel economy worked out to 27.4 miles per gallon. On the third attempt, we drove at an average speed of 69.9 mph for 15.6 miles. Fuel economy was 28.2 miles per gallon.
The second and third attempts are more likely in line with real world performance since they were not carried out with powerful tailwinds. Averaging the results gives a fuel economy of roughly 27.8 mpg.
|Attempt 1||Attempt 2||Attempt 3|
|Distance Driven (Miles)||15.4||15.2||15.6|
|Average Speed (MPH)||69.8||68.5||69.6|
|Fuel Economy (MPG)||32.8||27.4||28.0|
The EPA, meanwhile, officially rates the Suburban Diesel at 26 mpg on the highway, meaning that our results exceeded the EPA’s figures every time.
Turning to the specifics of our tester, the 2023 Chevy Suburban diesel SUV we drove is finished in the range-topping High Country trim level. The SUV rides on 22-inch Sterling Silver Painted Wheels with Chrome Inserts. It includes a panoply of optional features and upgrades, which you can read about in our original article about our Chevy Suburban diesel tester.
The optional 3.0L I6 LM2 turbodiesel baby Duramax engine develops 277 horsepower and 460 pound-feet of torque. Other powerplants available as part of the Suburban’s engine lineup include the naturally aspirated 5.3L V8 L84 gasoline engine producing 355 horsepower and 383 pound-feet of torque, and the naturally aspirated 6.2L V8 L87 gasoline engine, rated at 420 horsepower and 460 pound-feet of torque.
All three of these Chevy Suburban diesel and gasoline engines are mated to the GM 10-speed automatic transmission, with both RWD and 4WD available. Our tester has the 4WD configuration.
Under the body panels, the 2023 Chevy Suburban diesel SUV rides on the long wheelbase version of the GM T1 platform, an underpinning it shares with other extended-length GM full-size SUVs including the GMC Yukon XL and the Cadillac Escalade ESV. Production of the Suburban takes place at the GM Arlington plant in Texas.
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Odometer was at 2400 miles. This will improve 2-3 mpg once properly broken in and after the first oil change
The small diesel would be the only engine I’d trust. The v8’s have known
problems with their dfm systems.
I could see getting one of these, but we decided to get a new HD instead. We will be running our 2015 Suburban 5.3 into the ground.
So why were you testing this vehicle in auto 4wd in Florida vehicle should have been in 2wd for fuel mileage test run. I have this suv but with the 6.2l it gets 26 mpg was my best in 2wd.
That icon is confusing… it means auto, which for the most part means 2WD / RWD. It doesn’t stand for Auto 4WD.
“Auto” means the front hubs are engaged (creating a lot of drag), but the transfer case isn’t – until slippage is detected. In my Sierra 6.2/8A, I see a 2 mpg penalty in “auto” vs. “2WD.”
Iron pistons instead of forge aluminum ?
Negative. Hyperteutic aluminum alloy. This is the LM2, or original 3.0 duramax
The new LZ0 features Steel pistons. However, I don’t have specs on these. Don’t know the weight, pin height, ring spacing s, ETC. Steel pistons are by far superior. They don’t expand as much and retain more heat in the combustion process, which also keeps engine temps down. Only problem is that they are expensive to make, and machining them takes way longer than aluminum alloy pistons. Race pistons use steel because the strength allows them to machine them lighter than aluminum, though GM probably isn’t going to spend 12 hours machining each piston. The steelies are probably a little lighter due to a slightly reduced bore. IDK if any modern engine running iron pistons
I want the LZ0 in my next full-size SUV, but despite several different sites on the interwebs saying the 2024 refreshed full-size GM SUV’s will get it, locally my dealer is telling me FIRST they’re gonna continue installing the LM2 until the surplus of built engines is consumed, THEN they’ll offer the LZ0.
(Probably quite a awhile later)
I sure hope they’re wrong…
**By the way Steven (my name too) I don’t have exact specs on the new steel pistons, but I do remember an interview with one of the engineers where he said the new steel pistons are shorter (stronger) so to maintain the same stroke, they lengthened the connecting rod. They also redesigned the piston combustion bowl.
To me this is a highly inaccurate testing method. Drive 15 miles the give a reading off the computer???? Get real. Fill the tank and run it until you get down to a quarter tank and the refill it. Do thaf three times and get acreal world mileage estimate not one done by a computer.
Not necessary to run a full tank of gas to get fuel economy, however the most accurate test would be at least a 50 mile test. Topping off the tank before testing, run the 50 miles and return to the same pump and fill the same way. Then divide miles traveled by gallons used. Using the onboard dash computer you have to keep in mind “computers don’t lie, but liars program computers” and I’ll guarantee GM signed his paycheck so he is very likely to program the computer in favor of his employer.
Thank you both for the feedback.
Our testing involved driving 15 miles three times, which is very close to the 50 mile figure you’ve recommended.
As for your recommendations about testing, every single owner or driver will use the DIC for the fuel economy performance, and trust it. The conspiracy theories about computers lying likely made sense in the 90s or early 2000s, but are irrelevant today. Hence, our testing involves what owners will be able to see and observe themselves.
I’D LIKE TO SEE SOME TOWING SPECS. TO COMPARE TO MY GMC YUKON DENALI TO SEE HOW IT HANDLES THE LOAD TO COMPARE IT TO THE 6.2. WHICH GETS 9 MILES TO THE GALLON PULLING ALMOST 9,000LBS, CAR AND ENCLOSED TRAILER.
The refreshed 3.0 LM0 will pull similar to the 6.2 but with better fuel economy.
The fuel economy of a diesel engine is not impacted as much as a gasoline engine is when towing largely because the diesel hits its peak torque at a lower rpm than a comparable gasoline engine. The 6.2 gas engine and the 3.0 duramax both have comparable torque numbers but the diesel hits its peak torque at half the rpm.
Diesel’s also tolerate heat better than gas engines – towing makes a lot of heat which can lead a gas engine to run a little richer.
Short distances are meaningless for a vehicle with a 500 mile range.
I own a ‘22 RST suburban 4WD with the diesel. I have 15k miles on it in one year. In city driving I never get less than 20mpg. On the highway I have generally returned 25.5mpg on my 300 mile trips from Dallas to west Texas. I can and have gotten better than 27 when I drive closer to 70mph or have favorable winds. When I drive further west into New Mexico I often fight a headwind and see 19-20mpg at highway speeds. My gasoline powered 1/2 ton quad cab truck would get 14 in similar conditions for reference.
Thanks for the informative post.
Great information Thanks
Give us some real world testing. Load the seats and cargo area with sand bags to simulate passengers and cargo the hook a 7000 pound travel trailer on the back of it and run it between Denver Colorado and Grand Junction, Colorado. Then fuel it up and head back to Denver. Most people buying suburban do not drive them around with just the driver and no other payload. Show us what it will really do.
Actually, most Tahoes and Suburbans run most of the time with one or two passengers. These are like trucks – some are bought for the idea, not for the purpose.
The TFL guys in Colorado do mileage testing kinda like this, but they don’t go into the mountains, instead they did a 66 mile loop on I-25 pulling a 7000 pound trailer and got 14 MPG from a 2021 Suburban High Country Diesel with (I think) just the Driver.
Video was difficult to listen to and why test the old engine?
Are you hard of hearing? Video seemed well done to me and presentation was good, clearly explaining the test and results.
Old engine? The new LZ0 isn’t going into these until the 2024 model year, which sent even been announced yet.
Well, the image of a dinosaur is that it is large. Imagine how driving will have changed by the time this huge SUVs are junked.
3.0 l How many miles do injectors last estimate cost to replace injector anyone know?
based on your driving. Diesel is like a baby even though the sound is like monster.
Today’s clean diesels are better for the environment than mining an EV battery, but not as clean as a fuel cell.