GM’s New Mongoose 8.3-Liter Duramax Diesel Makes 555 HP, 1,230 LB-FT

• The new 8.3-liter Duramax turbodiesel V8 produces 555 horsepower and 1,230 pound-feet of torque.
• Dubbed The Mongoose, this engine will be available in the 2027 Chevrolet Silverado HD and GMC Sierra HD.
• The maximum towing capacity is 38,000 pounds for trucks equipped with a proper gooseneck setup.

The mighty Mongoose engine was revealed a few days ago. General Motors promised an engine ready to devour Ford's Power Stroke, which has the in-house codename "Scorpion." The numbers have arrived, and GM's new mill certainly boasts Blue Oval-besting power figures.

The all-new Duramax 8.3-liter turbodiesel V8 produces 555 horsepower and 1,230 pound-feet of torque. Those figures easily trump the output of the outgoing 6.6-liter Duramax, which delivers 470 hp and 975 lb-ft of torque.

More importantly, of course, the Mongoose also bests the Scorpion. Ford's Power Stroke is rated to produce 500 hp and 1,200 lb-ft of torque. Gargantuan numbers, to be sure, but no longer a best-in-class statement piece.

2027 GMC Sierra HD

Photo by: General Motors

Which Trucks Will Get The 8.3-Liter Duramax?

General Motors will offer the new V8 on the 2027 Chevrolet Silverado HD and the GMC Sierra HD. That gives both trucks a conventional max tow rating of up to 20,000 pounds when properly equipped. But when you have a gooseneck setup in the bed, that figure rises to a massive 38,000 pounds.

Both trucks feature a new electronic power steering setup. GM says this allows for more precise steering feel, reduced kickback, and quieter operation. The brakes have been upgraded to a larger size and a four-piston front caliper setup.

And each truck benefits from improved turbo technology and cooling features. Both rigs should prove extremely capable haulers.

Per GM, both trucks should begin arriving on dealer lots later in 2026. As we get closer to that time, we'll learn how much it will cost to stuff the 8.3-liter Mongoose into the snout of these pickups.

Motor1's Take: While GM couldn't have picked a worse time to launch a massive new diesel engine, there will always be a market for these trucks. People need to tow and haul, and a properly set up heavy-duty truck remains the best way to do that.

Plus, truck owners love having bragging rights over rival brands. With the Mongoose besting the Scorpion, Chevy and GMC shoppers will be smiling.

Until they have to take out their credit card at the pump and watch those numbers spin up faster than the turbo spools in that fancy new truck.

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