6.2L GM/Detroit Diesel

6.2L Diesel Specs, History, & Info

The 6.2L GM (6.2L Detroit, alternatively) was produced by Detroit Diesel and found in 1982 to 1993 model year GMC and Chevrolet pickups. It was available in 1/2 ton through 1 ton applications (C/K 10, 20, 30), which included SUVs such as the Blazer and Suburban. The primary motivation in the 6.2 diesels development was to produce a fuel efficient engine alternative for the period's gas guzzling small and big block V-8s. In terms of fuel economy, the 6.2L met expectations perfectly, allowing full-size pickups to achieve low and mid 20 miles per gallon. The engine was never intended to top the charts in terms of capability, and thus struggled to compete in this category as Ford and Dodge rolled out medium duty engine platforms in their respective 3/4 and 1 ton pickup models. GM would eventually develop the 6.5 Detroit based on the 6.2 design, and ultimately retire the IDI Detroit diesels altogether in favor of a more powerful, more reliable, technologically savvy 6.6L Duramax.

The 6.2L diesel was introduced for the 1982, following the retirement of Oldsmobile's 5.7L diesel. The 6.2 was manufactured by Detroit Diesel, a division of General Motors at the time. GM never intended for Detroit's 6.2L diesel to perform the heavy lifting. They wanted an engine that could haul hay to, from, and around the ranch while consuming as little fuel as possible. Additional, the robust design of a diesel would mean the engine would outlast a comparable gasser. Properly tuned and maintained, the engine was good for fuel economy figures well into the 20's; hard to beat with a small block gas V-8 choked down by emissions equipment. Being naturally aspirated, the 6.2L diesel has a relatively high compression ratio. The heart of its injection system is the Stanadyne DB2 injection pump, the same pump used on the 5.7L Olds, International's 6.9L/7.3L IDI, and the later 6.5L diesel. 6.2L diesel engine block's and cylinder head's were produced from cast iron. Interestingly, the engine was offered in 1/2 ton, 3/4 ton, and 1 ton GMC/Chevrolet pickups, as well as Blazer and Suburban models. As a result, GM is considered the original pioneer of 1/2 ton diesel in the United States, although credit is often given to Ram Trucks for the introduction of the "EcoDiesel" for their 2014 model year Ram 1500 pickup.


6.2L Diesel Transmission Options

The original 6.2L came mated to either the TH400 three speed automatic, Muncie SM465 four speed manual transmission, or New Process NP833 four speed manual overdrive transmission. The 6.2 shares its bellhousing pattern with GM V-8 gas engines - a diesel transmission will bolt up to a gas engine with no modifications and visa versa. The diesel automatic transmissions typically used a different torque converter than the gas engine automatics, although there seems to be some exceptions (which relate to the truck's GVWR) in which this is not the case. If swapping transmission from gas to diesel, it is best to acquire the torque converter specific to your application. The Muncie SM465 is much more common than the New Process NP833, which features an 0.73 to 1 overdrive in comparison to the SM465's 1 to 1 top gear. The NP833 can be identified by transmission RPO code "MY6". Later 6.2L GM diesels were available with the 700R4 and 4L60E overdrive automatic transmissions as they became available and were integrated into their platforms.


6.2L GM/Detroit Diesel Specs


Detroit 6.2L V-8 diesel

Years Available:

1982 to 1993 model years


6.2 liters, 379 cubic inches

Compression Ratio:

21.5 : 1


3.98" (101 mm)


3.82" (97 mm)


Naturally aspirated (no turbocharger)


Indirect injection (IDI), Stanadyne DB2 rotary injection pump


Overhead valve (OHV), 2 valves per cylinder

Oil Capacity:

7 quarts with filter

Engine Weight:

650 lbs dry

Max Engine Speed:

3,600 rpm (4,000 rpm w/ no load)

Peak Horsepower:

Introduced at 130 hp @ 3,600 rpm, maximum offered during production was 143 hp @ 3,600 rpm. The United States Army's version was rated at 165 hp @ 3,600 rpm.

Peak Torque:

Introduced at 240 lb-ft A 2,000 rpm, the maximum offered rating during production was 257 lb-ft @ 2,000 rpm. The United States Army's version was rated at 330 lb-ft @ 2,100 rpm.


The 6.2L diesel was ordered with regular production option codes (RPO) LH6 (C series) and LL4 (J series). Many vehicles employed by the United States' Army were powered by the 6.2L diesel, from pickups to HUMVEES. The Army version had a higher output rating of 165 horsepower and 330 lb-ft of torque, quite an increase over the production engines. While there are a number of high mileage examples, the 6.2L suffers from many reliability issues, including cracks forming and propagating in the engine block, flywheel, harmonic balancer. Overall, the engine has not been particularly popular, but had its place in the market and a moderately sized following, even today. A popular trend is to acquire an 80's 6.2L diesel powered half ton and swap in a built gas engine. The 1980's diesel chassis does not require any emissions inspections in states that require periodic inspections, and fans of the 1973 to 1987 body style can modify the trucks as much as they want without running into registration issues. This is an alternative to finding a 1975 or older chassis, which limits the pool of trucks to choose from (pre 1976 trucks do not require SMOG inspections in CA and states with similar laws). If searching for a used truck powered by the 6.2L diesel, it is quite common to come across ads for trucks that have undergone such transformations.