GM names its next-gen HD diesel "Mongoose", an all-new 8.3-litre Duramax V8
Why it matters: This replaces the L5P that has powered Chevrolet/GMC heavy-duty diesel pickups since 2020, and confirms both the name and displacement for the first time, a direct shot at Ford's coming Super Duty diesel.
General Motors has confirmed the codename and headline spec of its next heavy-duty diesel: an all-new 8.3-litre turbo-diesel V8, nicknamed "Mongoose" internally and badged Duramax L6P in GM's own fleet order guide. It lands in the 2027 Chevrolet Silverado HD and GMC Sierra HD (2500 and 3500 models), paired with Allison-branded 10-speed automatics, replacing the L5P. GM's teaser is long on branding, "built to dominate", and short on numbers: no horsepower or torque figures released yet, with GM saying only "Chevy and GMC will have more to share soon." The order guide itself had already listed the L6P as an available option before this public confirmation.
Source: GM News · 21 September 2026