General Motors officially announced the next generation 8.3 liter Duramax V-8 diesel engine in a short video posted to the media hosting platform YouTube on September 21st, which was shared via GM's official news channel. The animated video labels the new engine "Mongoose" and painted a clear picture that GM was seeking superiority over Ford's "Scorpion" 6.7 Power Stroke.
GM released additional details on September 24th, 2026, including that the new engine would be rated at a peak 555 horsepower and 1,230 lb-ft of torque. This beats the current Ford Power Stroke by 55 horsepower and 30 lb-ft of torque and Ram's 6.7 Cummins Turbodiesel by 125 horsepower and 155 lb-ft.
Applications
The 8.3 liter Duramax will be available in the 2027 Chevrolet Silverado 2500/3500 HD and GMC Sierra 2500/3500 HD pickup trucks alongside a revamped 6.6 liter gasoline V-8. According to the 2027 order guide, the engine will also be used in the Silverado/Sierra 3500 HD chassis cab.
GM has not confirmed whether the 8.3 Duramax will be used in the Silverado 4500/5500/6500 HD chassis. Since 2017 the 3500 HD chassis cab has used the same 6.6 liter Duramax L5P engine that is used in pickup truck models. Alternatively, the 4500/5500/6500 medium duty chassis has used the 6.6 Duramax L5D, a de-rated commercial version of the L5P, since 2019. International has also used the L5D in several of its medium duty models, which have been produced through a joint venture with General Motors.
Engine Architecture
The 8.3 liter Duramax is a V-8 engine with a compacted graphite iron (CGI) engine block. Its cylinder bore diameter and stroke length have not yet been revealed. It utilizes a forged steel crankshaft, connecting rods, and pistons.
Emissions & Displacement
More stringent emissions regulations go into effect for 2027 model year vehicles and it is no coincidence that the 8.3 liter platform is launching on this timeline. The 8.3 Duramax is representative of GM's approach in applying more efficient technologies and strategies to meet current and future emissions regulations.
2027 introduces a new set of challenges for automakers in that they address "emissions from frequently encountered vehicle operating conditions not previously captured in EPA test procedures" [1] This includes a closer evaluation of vehicle emissions while the engine is below normal operating temperature.
In this instance adopting a larger engine displacement is a major component of the emissions strategy. At a given power level, the engine will operate at lower cylinder pressures and produce less heat than a smaller displacement engine would. Merging this with a much more efficient engine design - airflow, injection, and combustion improvements - and a streamlined after treatment strategy is a recipe for lower NOx and PM emissions.
[1] - from the U.S. Environmental Protection Agency's "Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles: Final Rule" regulatory announcement, publication EPA-420-F24-016, dated March 2024.
Engine Specs
| Names | 8.3 Duramax, Mongoose, Duramax L6P, L6P Duramax |
|---|---|
| RPO Code(s) | L6P |
| Engine Family | Duramax 8300 [2] |
| Manufacturer | DMAX Ltd/General Motors |
| Assembly Plant(s) | DMAX engine plant in Brookville, OH |
| Type | 4 cycle diesel, turbocharged, liquid cooled |
| Configuration | V-8 |
| Applications | 2027 Chevrolet Silverado 2500 HD, 3500 HD 2027 GMC Sierra 2500 HD, 3500 HD |
| Displacement (nominal) | 8.3 liters, 506 cubic inches |
| Bore | TBA |
| Stroke | TBA |
| Compression Ratio | TBA |
| Engine Block Material | Compacted graphite iron (CGI) |
| Cylinder Head Material | TBA |
| Injection System | Direct injection, high pressure common rail |
| Injection Pump | TBA |
| Injection Pressure | Up to 39,000 psi |
| Aspiration | Turbocharged and intercooled Dual-stage air-to-water charge air cooler |
| Turbocharger | Variable geometry |
| Reciprocating Assembly | Forged steel crankshaft, connecting rods, and pistons |
| Valvetrain | Traditional cam-in-block pushrod V-8 |
| Engine Oil Capacity | TBA |
| Oil Pump Type | Electronically controlled variable displacement |
| Power | 555 horsepower @ 2,500 rpm |
| Torque | 1,230 lb-ft @ 1,400 rpm |
| Coupled Transmissions | GM "Allison" 10L1000 ten speed automatic |
[2] - Assumption based on prior patterns
Competitive Comparison
Ford's High Output 6.7 Power Stroke, the "Scorpion", is rated at a peak 500 horsepower at 2,600 rpm and 1,200 lb-ft of torque at 1,600 rpm. Ram's High Output 6.7 Cummins Turbodiesel, which underwent a significant redesign for the 2025 model year, is rated at 430 horsepower at 2,800 rpm and 1,075 lb-ft at 1,800 rpm. At 555 horsepower and 1,230 lb-ft of torque, the 8.3 Duramax is rated at 55 horsepower more than Ford's Power Stroke and 125 more than the Cummins. With regard to torque, the new Duramax bests the Power Stroke by 30 lb-ft and the Cummins by 155 lb-ft.
Editor, Diesel Hub