General Motors recently introduced the 3.0-liter LZ0 Duramax Diesel, which is the second-generation of the inline 6-cylinder turbo Diesel engine Chevrolet brought to market in 2019. The first-gen LM2 diesel is currently used in a variety of GM vehicles including the GMC Sierra, Chevy Tahoe, GMC Yukon and Cadillac Escalade. It’s been a nifty little engine, but it’s also been beset with quality issues and a questionable design.
In an exclusive interview John Barta, Chevrolet assistant engineer for diesel engines, we now know more about the new LZ0 engine, including some juicy details about the extended belt life and the pesky long crank, slow start issues.
Barta says about 25% of the parts on the LZ0 are different. The biggest change: steel pistons. These new steel pistons are narrower than the previous aluminum ones, which allows the piston stroke to be longer. That combined with new injectors allowed the engineers to retune the turbocharger to deliver more power. Torque is up 7.6% and horsepower is up 10%.
The big benefit of the LM2 was you could hit the maximum torque of 460 pound-feet at 1,500 RPMs. Hitting the torque at such a low RPM is what gives you the “throw you back in the seat” feel. Though Barta says the new LZ0 has a longer torque curve, reaching 490 pound-feet at 2,750 RPMs, you still get the 460 pound-feet at 1,500 RPMs. Basically, you still get the whiplash effect but also more power when passing and towing.
Other changes include the use of two actuators instead of three, updated engine cooling and a different cylinder head.
Those who’ve grumbled over the oil belt location at the rear of the LM2 engine may be interested to know you can now drive the truck for about 20 years without needed to inspect the belt with the LZ0 engine. This is a big deal since the location of the belt requires you to drop the transmission to inspect it. Not an easy afternoon DIY job.
The LZ0 Duramax Diesel inspection recommendation has been extended to 200,000 miles.
Barta knows the location of the belt as it has become a hot topic, and he said moving the belt to the front of the block would require a complete redesign of the engine. Plus, if the belt is moved, it would take away the good reasons they had for putting in the back of the engine block.
If you aren’t aware, the previous LM2 engine had reports of a long crank and either a slow-start or no-start event. If you waited a few moments and tried again, the truck would usually start up.
Barta said this was a difficult problem to track down since most dealers couldn’t replicate the issue, and during GM’s testing, it never came up. After several man hours, however, the engineers discovered it was a supplier issue. The culprit: An exciter wheel with bent teeth, which would trick the system into thinking it wasn’t operable.
GM fixed the supplier issue as well as changed the engine crank to allow the teeth to better engage in both the LM2 and LZ0 engines. Thus, Barta said there are no concerns of this happening on the LZ0 Duramax Diesel engine, and the current diesel is also fixed.
While official fuel economy numbers haven’t been released yet, Barta said the numbers should be fairly close to the existing numbers for the LM2. For reference, the current diesel with 2WD is rated at 31 MPG on the highway, 4WD models get 26 MPG on the highway. However, in personal testing, we’ve seen real-world numbers that are often higher.
Because this is the perennial question, of course, we asked if a diesel hybrid were on the horizon. Without giving away future product information, Barta did say it is a consideration.
Since we recorded the interview, you can catch the full discussion — including more details — on our YouTube channel.
With electric vehicle news dominating the headlines recently, we’re glad to see the diesel engine for light-duty trucks and SUVs isn’t dead.
Plus, the belt-life inspection recommendation and long-crank fix with the LZ0 Duramax Diesel is a big deal. Hopefully, we will get to drive a truck with this engine soon!
So if the belt snaps before 200k miles will GM stand behind and repair damaged engine?
Anything on towing capacity? Why do you think not all trims with this engine offer the max towing package?
What about the main rear seal fix??
What a horrible place to put a belt. Millions of engines and no one until now said lets put the ticking time bomb in the back of the oil pan. Just another ( VERY ) expensive repair if you do it on time, and a new engine if it breaks.
Do you know what trim levels for the GMC Sierra 1500 the LZ0 will be available for?
I have a question. I just received my 2023 GMC Denali LZ0 and love it so far. The more I read it says diesel fuel is notoriously inconsistent (especially in the U.S.). I see Canada and the U.S. try to keep the ctain at 40 while Europe is 50. I see they ( the LZ0) don’t require additives. Will something like Hot Shots Secrets EDT help/hurt this new system? It says it’s a ctain booster as well as a cleaner. I live in Canada and the fuel is supposedly a little more consistent but am planning a driving trip to Florida this winter. Will this trip require an additive for American fuel?
Sorry for the bad spelling! ctain = cetane!