Ask TFL: Will GM Build a 6.0L Straight-Six Duramax HD Diesel For Bigger Trucks?

What is the future of GM heavy duty diesels?

2020 gmc chevy sierra silverado 3500 hd new duramax diesel

Will General Motors design and build their own straight-six heavy duty diesel engine? It can be a 6.0-liter displacement or bigger and easily hit 1,000 lb-ft of torque. This is based on a question we recently received from Adam S, a TFLtruck viewer.

Adam writes:

With the 3.0L straight six Duramax being so well received in the full size half-ton market, do you think there is any possibility GM will release a straight six configuration in the heavy duty class?  Also, Ram + Cummins + Allison would be a major $$$ win for FCA.

There is no information that suggests that GM is currently working on a whole new turbo-diesel Duramax engine for their heavy duty trucks. There is not insider source with this information at this time.

Still, Adam brings up a very interesting topic. What’s next for the big 6.6-liter Duramax V8 that is currently being used in the 2020 Chevy Silverado HD and Sierra HD trucks? Will GM give the well-respected V8 another update soon or is it time for something completely new?

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2.7-liter I4 turbo gas

GM has recently been on a roll with new truck engine introductions. They recently introduced a 2.7-liter I4 gas turbocharged engine in their Silverado 1500 and Sierra 1500 trucks. This is a very high-tech engine with a new turbocharger inlet design, different cam profiles (including cylinder deactivation), and a new coolant management system. The current output on this engine is 310 hp @ 5,600 rpm and 348 lb-ft of torque @ 1,500 rpm.

3.0-liter I6 turbo diesel

There is also the aforementioned 3.0-liter I6 turbo-diesel Duramax engine that earned our 2020 Gold Hitch best towing half-ton diesel award. The new diesel has even power delivery and a great 33 MPG highway rating by the EPA. The power output stand at a class-leading 277 hp @ 3,750 rpm, while the torque is also a good (but not class-leading) 460 lb-ft @ 1,500 rpm.

What if GM developed a heavy duty version of the straight-six diesel engine? What displacement would it have and how much power would it deliver? Let us know in the comments section below.

  • Yes, GM should build and sell an all-new HD I6 Duramax.
  • No, they should further refine the 6.6L V8 Duramax.

In my personal opinion, a new straight-six makes a lot of sense. If GM can maintain that smooth power delivery we see in the 3.0-liter I6 and provide good economy and emissions performance – yes! It should be possible to get the horsepower close to 500 hp and the torque to over 1,000 lb-ft.