As we speed toward the 25th anniversary of the Duramax diesel engine, let us take a moment to reflect on the astonishing history of this pivotal heavy-duty engine. The story begins in 1996 as General Motors was finalizing plans for its next-generation of light- and heavy-duty pickups. The company knew it needed a new, modern diesel engine in order to compete with the likes of Dodge’s 5.9-liter Cummins and Ford’s 7.3-liter Power Stroke.
GM executives turned to their partners at Isuzu, a leader in global heavy-duty diesel engines, to help with the project. The first running prototypes of the new 6.6-liter V8 engine were completed in Japan in 1998. In September of the same year, a new joint venture was formed between General Motors and Isuzu called DMAX Ltd. The new venture’s headquarters and manufacturing were established in Moraine, Ohio.
While each 6.6-liter Duramax diesel engine produced has shared the same basic architecture and displacement, a lot has changed through the years. Telling the engines apart is simple once you know either its VIN (eighth position) or RPO code (LBZ for example), as the engines often spanned multiple body generations.
Each Duramax engine generation is commonly referenced by its RPO code, which is GM parlance for Regular Production Option. These three-digit alpha-numeric codes guide each vehicle through the production process and apply to nearly all options, including paint, suspension, and axle types, in addition to drivetrain.
Over the course of a quarter-decade, the company has produced more than two million 6.6-liter Duramax diesel engines, and DMAX Ltd. is now wholly owned by General Motors.

Duramax 6.6L turbo-diesel V8 engine, introduced in 2001, featured four valves per cylinder and direct injection. It was rated at 300 horsepower and 520 lb-ft of torque.
LB7 Duramax Engine Specs
Years Produced: 2001-2004
VIN Code: 1
Displacement: 403 cubic inches, 6.6-liters
Compression Ratio: 17.5:1
Firing Order: 1-2-7-8-4-5-6-3
Bore: 4.055 inches (103mm)
Stroke: 3.897 inches (99mm)
Aspiration: IHI RHG6 turbocharger
Injection: Bosch high-pressure common-rail with CP3 injection pump
Engine Weight: 835 pounds (approx.)
Horsepower: 300 @ 3,100 RPM
Torque: 520 @ 1,800 RPM
LLY Duramax Engine Specs
Years Produced: 2004.5-2005
VIN Code: 2
Displacement: 403 cubic inches, 6.6-liters
Compression Ratio: 17.5:1
Firing Order: 1-2-7-8-4-5-6-3
Bore: 4.055 inches (103mm)
Stroke: 3.897 inches (99mm)
Aspiration: Garrett GT3788VA variable geometry turbocharger
Injection: Bosch high-pressure common-rail with CP3 injection pump
Engine Weight: 835 pounds (approx.)
Horsepower: 310 @ 3,000 RPM
Torque: 520 @ 1,600 RPM
LBZ Duramax Engine Specs
Years Produced: 2006-2007.5
VIN Code: D
Displacement: 403 cubic inches, 6.6-liters
Compression Ratio: 16.8:1
Firing Order: 1-2-7-8-4-5-6-3
Bore: 4.055 inches (103mm)
Stroke: 3.897 inches (99mm)
Aspiration: Garrett GT3788VA variable geometry turbocharger
Injection: Bosch high-pressure common-rail with CP3 injection pump
Engine Weight: 835 pounds (approx.)
Horsepower: 360 @ 3,200 RPM
Torque: 650 @ 1,600 RPM
LMM Duramax Engine Specs
Years Produced: 2007.5-2010
VIN Code: 6
Displacement: 403 cubic inches, 6.6-liters
Compression Ratio: 16.8:1
Firing Order: 1-2-7-8-4-5-6-3
Bore: 4.055 inches (103mm)
Stroke: 3.897 inches (99mm)
Aspiration: Garrett GT3788VA variable geometry turbocharger
Injection: Bosch high-pressure common-rail with CP3 injection pump
Engine Weight: 835 pounds (approx.)
Horsepower: 365 @ 3,100 RPM
Torque: 660 @ 1,800 RPM
LML Duramax Engine Specs
Years Produced: 2011-2016
VIN Code: 8
Displacement: 403 cubic inches, 6.6-liters
Compression Ratio: 16.0:1
Firing Order: 1-2-7-8-4-5-6-3
Bore: 4.055 inches (103mm)
Stroke: 3.897 inches (99mm)
Aspiration: Garrett GT3788VA variable geometry turbocharger
Injection: Bosch high-pressure common-rail with CP4 injection pump and Piezo injectors
Engine Weight: 835 pounds (approx.)
Horsepower: 397 @ 3,000 RPM
Torque: 765 @ 1,600 RPM

The all-new 2017 Duramax 6.6L turbo diesel features more torque and horsepower and increased strength cylinder block, heads, crankshaft, connecting rods and pistons. The Duramax features a state-of-the-art oil separator and cold-start system among other features.
L5P Duramax Engine Specs
Years Produced: 2017-Current
VIN Code: Y
Displacement: 403 cubic inches, 6.6-liters
Compression Ratio: 16.0:1
Firing Order: 1-2-7-8-4-5-6-3
Bore: 4.055 inches (103mm)
Stroke: 3.897 inches (99mm)
Aspiration: Borg-Warner variable geometry turbocharger
Injection: Desno high-pressure common-rail with HP4 injection pump and G4S Gen III solenoid-type injectors
Engine Weight: 800 pounds (approx.)
Horsepower: 445 – 470 @ 2,800 RPM
Torque: 910 – 975 @ 1,600 RPM