GM's 8.3-litre Mongoose diesel makes more power by working less
Every Duramax V8 since 2001 has displaced 6.6 litres, and the Mongoose breaks that rule
General Motors has given its heavy-duty pickups a diesel V8 of 8.3 litres. Called Mongoose, the new Duramax makes 555 hp and 1,668 Nm in the 2027 Chevrolet Silverado HD and GMC Sierra HD, more than any diesel Ford or Ram puts in a pickup. It is the largest V8 GM has fitted to a pickup, bigger even than the 8.1-litre Vortec petrol of 2001, and it arrives with American diesel above $6 a gallon.
The 8.3-litre Duramax Mongoose makes 555 hp and 1,668 Nm
The Mongoose replaces the 6.6-litre L5P, which made 470 hp and 1,322 Nm, so the gain is 85 hp and 26 percent more torque. Its block is compacted graphite iron, lighter and stronger than the grey iron of the old engine, and the crankshaft, connecting rods and steel pistons are all forged. A variable-geometry turbocharger feeds a dual-stage air-to-water charge cooler, and an Allison 10-speed automatic takes the output. The trucks go on sale at the end of 2026, eight days after GM showed new small-block petrol V8s for its half-ton Silverado, and prices are still to come.
The Mongoose makes 67 hp per litre, less than the 6.6-litre it replaces
The Mongoose makes 67 hp per litre, against 71 for the L5P it replaces and 75 for Ford's 6.7-litre Power Stroke. Torque per litre barely moves: about 200 Nm, the same as the old engine. GM has spent the extra 1.7 litres on lowering the load on each cylinder rather than on a higher specific output, the opposite of the downsizing logic European engineers followed for two decades. For a truck that spends its working life towing near its limit, less stress per litre is the more durable route, and the forged internals show GM expects owners to lean on it.
Ford's Super Duty still out-tows the Silverado 3500HD, 18,144 kg to 17,237 kg
GM now tops the diesel power table: Ford's 6.7-litre Power Stroke makes 500 hp and 1,627 Nm, and the Cummins in the Ram Heavy Duty 430 hp and 1,458 Nm. It does not top the towing table. A suitably specified Silverado or Sierra 3500HD pulls 17,237 kg on a gooseneck hitch and 9,072 kg on a conventional one, while Ford rates its Super Duty at 18,144 kg. GM last led on diesel power when the L5P arrived in 2017, and Ford overtook it the following model year. The HD trucks also switch to electric rack-and-pinion steering, a first in the segment.
Mercedes sold the first diesel car 90 years ago, and the EU now buys 7.3 percent
Diesel took 7.3 percent of new EU car registrations from January to August 2026, down from 9.4 percent, and diesel volumes fell 18.6 percent, according to ACEA. That is the market the Mercedes-Benz 260 D, the first series-production diesel car, has left behind in its 90th year. The biggest diesel ever sold in a European passenger car, the 6.0-litre V12 TDI in the Audi Q7, made 500 hp and 1,000 Nm and left the range in 2012. When Stellantis brought diesel back to the Peugeot 308 and Opel Astra, it used a 1.5-litre with 130 hp; the Mongoose is five and a half times that size.
A Silverado HD in Europe weighs more than a B licence allows
GM does not sell the Silverado HD or Sierra HD in Europe, so any that arrive come through independent importers. Their gross weight ratings sit well above 3,500 kg, the ceiling for a standard European B licence, which means driving one legally here needs a C1 licence. Fuel is the other barrier on both sides of the Atlantic: US diesel passed $6 a gallon for the first time on 10 September, and European pumps have been setting their own records in the same weeks.
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GM has built the right engine for the job, and built it conservatively. Every litre of the Mongoose works less hard than a litre of the Power Stroke it is chasing, and the forged bottom end and compacted graphite block are there for the owner towing 17 tonnes through a Texas summer, not for the brochure. Europe spent twenty years squeezing more from less. GM has taken the older route, and for a work truck it is the better-engineered one.
Ford needs 41 Nm to take the torque title back, a gap a calibration change can close, and it overtook GM within a model year last time. Expect a higher-rated Power Stroke before the 2028 trucks are priced. The result that matters more will take years: whether the Mongoose reaches 500,000 km on its original turbocharger and injectors. With this much displacement doing this little work per litre, it should.
