Duramax FAQ

Frequently Asked Questions about the Duramax Diesel

Answers to frequently asked questions about the 6.6L Duramax diesel, which has been offered in six variations over the course of more than a decade. To this day, the Allison 1000 remains the automatic transmission of choice for Duramax owners. The GM-Isuzu relationship, DMax, Duramax assembly plants, block heater location, DEF, and more are all answered below.

Who developed the Duramax Diesel?

The 6.6L Duramax diesel is the result of a joint venture between General Motors and Isuzu named DMAX Ltd, which was announced in December of 1998. The partnership allowed General Motors to take full advantage of Isuzu's expertise in developing and producing diesel engines. At the time, GM's 6.2L/6.5L Detroit diesel hadn't been near as successful as the company had hoped, but Isuzu had earned a favorable reputation, particularly in commercial and industrial markets. Reports indicate that Isuzu was primarily responsible for the engine's design, while GM's engineers were tasked with programming, calibrating, and integrated the engine's electronic systems in a manner suitable for their application. All Duramax diesels are assembled at the DMAX plant in Moraine, Ohio. GM is currently the majority stakeholder in DMAX, whom reportedly bought out Isuzu in 2002. The two company's have and continue to work closely on projects together.

How many versions of the Duramax exist?

Seven versions of the 6.6L Duramax 6600 engine have been produced to date:


Model Years



2001 - 2004



2004 - 2006

LLY replaced LB7 for mid-2004 model year.


2006 - 2007

LBZ and LMM offered for 2007 model year.


2007 - 2010

LBZ slowly discontinued through 2007 model year.


2011 - 2016

Current production engine.


2011 - 2016

Detuned engine for chassis cab pickups only.


2017 -

Replaced LML for 2017 model year

There are also the 7.8L and 2.8L Duramax diesels. The 7.8L Duramax is a medium duty, inline 6 cylinder engine identical to the Isuzu 6H series. The 2.8L Duramax is an inline 4 cylinder diesel available in the GMC Canyon and Chevrolet Colorado. Future diesels in General Motor's portfolio are likely to adopt the Duramax namesake.

My truck is from a transitional model year - which Duramax do I have?

Identifying your engine is as simple as looking at the 8th digit of your VIN number. See link: Which Duramax do I have

Why has the Duramax been changed so many times?

The evolution of the Duramax 6600 series has been necessary in order to meet emissions and remain competitive in the marketplace. Automakers are constantly battling for "Best in Class" and as a result, modifications and upgrades have been necessary in order to keep the engine modern and competitive. With each new iteration of the engine, we've seen enhanced features, higher performance, and a more coherent integration of powertrain systems.

Are the Duramax's aluminum cylinder heads as problematic as many people suggest?

NO! When the Duramax was introduced for the 2001 model year, it was the only diesel in its class to feature weight-saving aluminum cylinder heads. People tend to fear the unknown, and at the time the very concept of using aluminum cylinder heads was taboo. However, DMAX's design proved reliable and the cylinder head design is not a common source of problems or reliability concerns for any particular version of the 6.6L Duramax to date. Fast forward ten years, aluminum cylinder heads have become quite common on light to medium duty diesel engines, as have advanced materials for engine blocks.

What diesels were used in GMC/Chevrolet pickups before the Duramax?

In the late 70s, GM began offered the 350 Oldsmobile diesel in their cars and trucks. From a business standpoint, the engine was an utter failure, prompting GM to introduce the Detroit 6.2L IDI diesel in the early 80's. The goal was fuel economy, not performance or capability, and in this sense the 6.2L lived up to expectations. In fact, advertisements from 1982 suggest that a 2wd C10 pickup with the 6.2L diesel could achieve up to 30 miles per gallon on the highway. The engine was later modified into the 6.5L diesel - while more appropriate for 3/4 and 1 ton trucks, the engine was never particularly popular. In the wake of these trials, the 6.6L Duramax has been extremely successful and its popularity continues to grow.

What is DEF?

Diesel exhaust fluid (DEF) contains urea, the ingredient necessary for the selective catalyst reduction (SCR) system to convert nitrous oxides into less hazardous compounds. For additional information on SCR, DEF, and other emissions related components, see link: Duramax LML Emissions System Overview

Does my Duramax have a block heat? Where is the block heater?

All Duramax engines are factory equipped with an engine block heater. The block heater plug comes taped and/or zip tied to the wire loom traveling from the passenger side battery to the frame rail. Follow the negative battery cable and you'll bump right into it.

Where are Duramax engine's built?

All Duramax engines are assembled at the DMAX plant in Moraine, Ohio.