6.2L GM/Detroit Diesel

6.2L Diesel Specs, History, & Information

General Motors introduced the 6.2L Diesel for the 1982 model year. GM felt the need to add a fuel efficient alternative to their gas guzzling V-8's to the Chevrolet and GMC pickup brands. The resulting engine, manufactured by Detroit Diesel (a division of General Motors at the time), was not intended to be the workhorse of their engine lineup, but rather an economical alternative. If torque or towing was a primary concern, GMC/Chevrolet pickups could be ordered with a burly big block. The naturally aspirated 6.2L lived up to its expectations as a fuel sipper.

Farmers could haul hay and tools around the ranch without tearing deep into their pockets, and make it to the feed store on a budget. While the 6.2 diesel was no heavy hauler, it certainly appealed to a particular niche market. In the long run, the 6.2 would prove to have some reliability concerns including reoccurring overheating issues, cracked engine blocks, and failures of the harmonic balancer, crankshaft, and flywheel (the three of which are often related to one another). The 6.2L shares the same bellhousing bolt patterns and motor mounts as all GM V-8 gas engines, simplifying production and integration of the diesel power plant into C/K series pickups.

6.2L GM Diesel Specs


Detroit Diesel (a division of GM at the time)

Production Years:

1982 - 1993


GM/Chevrolet C/K trucks, Hummer H1, Jimmy, Suburban


90° V-8

Block/Head Material:

Cast iron engine block, cast iron cylinder heads


379 cubic inches, 6.2 liters

Firing Order:


Cylinder Numbers:

6.2L GM, Detroit diesel cylinder numbers


Early 1982 LL4

20.3 : 1

Late 1982+ LL4

21.3 : 1

LH6 (all years)

21.5 : 1


3.98 in (3.976 in, 101 mm)


3.82 in (3.8189 in, 97 mm)


• IDI (indirect injection)
• Mechanical injectors, Stanadyne DB-2 rotary injection pump


Overhead valve (OHV) pushrod engine (standard cam-in-block), hydraulic roller lifters


Naturally aspirated; factory turbocharger not offered

Nominal Dimensions:


29.5 in


27.2 in


27.4 in

Engine Oil Capacity:

7 qts w/ filter (use AC Delco PF35)

Engine Oil Spec:

SAE 30

ambient temperature > 32° F (preferred viscosity within temp range)

SAE 15W-40

ambient temperature > 0° F

SAE 10W-30

ambient temperature < 60° F

Fuel Requirements:

# 2 diesel

ambient temperature > 20° F

# 1 diesel

ambient temperature < 20° F, can substitute with winterized # 2 diesel fuel if necessary


engine not factory certified to run on biodiesel

Dry Weight:

Approx 700 lbs

Normal Operating Temp:

190 - 230° F

Idle Speed:

650 rpm (+- 25 rpm)

Max Engine Speed:

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

Peak Horsepower:

• 130 HP @ 3,600 rpm (introductory)
• 160 HP @ 3,600 rpm (peak)

Peak Torque:

• 240 lb-ft. @ 2,000 rpm (introductory)
• 275 lb-ft. @ 2,000 rpm (peak)

The 6.2L became available following the retirement of the infamous 5.7L Olds diesel. It was available in 1/2 ton as well as 3/4 and 1 ton model pickups, which is unique to GMC/Chevrolet because Ford and Dodge never offered diesels in their 1/2 ton pickups when they entered the diesel sector in 1983 and 1989, respectively. At an option of less than $1,500 and capable of surpassing some of GM's V-6 gas engines in fuel economy, the 6.2 diesel was an attractive offer. The engine's were Federally rated at up to 23 mpg combined and GM estimated up to 31 mpg on the highway. GM secured a government contract and provided 6.2L diesel engines and trucks to the United States Army in mass quantities, many of which can still be affordable purchased at government auctions. Despite some of the problems that plagued the 6.2L diesel in the long run, the engine ultimately achieved what GM/Detroit had set forth to do and paved the way for future endeavors in the diesel sector.

6.2L Diesel RPO Codes

RPO Code


Rated Horsepower

Rated Torque




1982 - 1989

130 HP @3,600 rpm

1982 - 1989

240 lb-ft @ 2,000 rpm

Light duty engine w/ exhaust gas recirculation (EGR), GVWR < 8,500 lbs

1990 - 1993

143 HP @ 3,600 rpm

1990 - 1993

257 lb-ft @ 2,000 rpm



1982 - 1984

135 HP @ 3,600 rpm

1982 - 1984

240 lb-ft @ 2,000 rpm

Heavy duty engine w/o exhaust gas recirculation (EGR), GVWR > 8,500 lbs

1983 industrial

145 HP @ 3,600 rpm

1983 industrial

240 lb-ft @ 2,000 rpm


160 HP @ 3,600 rpm


275 lb-ft @ 2,000 rpm

6.2L Diesel Horsepower & Torque Curves

6.2L GM diesel LH6 (light duty) horseower and torque curve

Horsepower and Torque curves/graphs for 1983 6.2L GM diesel LH6

6.2L GM diesel LL4 (heavy duty) horsepower and torque curves

Horsepower and torque curves/graphs for 1982 - 1985 6.2L GM diesel LL4

6.2L Diesel Engine Identification, Build Date

All 6.2L GM diesels have a 7 digit engine identification number stamped into the engine block below the intake runner of the number 1 cylinder. GM refers to this 7 digit sequence as the "broadcast code". An example of a broadcast code is as follows:

6.2L GM diesel engine ID example

Example of engine I.D. tag on a 6.2L GM Diesel

Suffix Letter

Model Year

Suffix Letter

Model Year













The broadcast code identifies the model year, build month, and build day.

6.2L GM Diesel Engine Oil Spec and Block Heater Schedule

Under normal operating conditions, the engine oil in a 6.2L GM diesel should be replaced every 5,000 miles or 12 months, whichever comes first. Under severe/heavy duty operating conditions, which includes periods of excessive idling, towing, and off-road driving (especially in dusty conditions), the engine oil should be replaced every 2,500 miles or 3 months, whichever comes first.

Oil Viscosity

Acceptable Temperature Range


SAE 30

ambient temperature > 32° F

preferred viscosity within listed temperature range

SAE 15W-40

ambient temperature > 0° F

acceptable viscosity within listed temperature range

SAE 10W-30

ambient temperature < 60° F

required cold weather viscosity

In addition to adhering to the engine oil viscosity chart above, the following block heater schedule should be used in cold weather:

Oil Viscosity

Ambient Temp > 32° F

Ambient Temp 32° F to 0° F

Ambient Temp < 0° F

SAE 30

block heater not required

use block heater min 2 hours

use block heater min 8 hours

SAE 15W-40

block heater not required

block heater not required

use block heater min 8 hours

SAE 10W-30

block heater not required

block heater not required

use block heater min 8 hours

Failure to use the engine block heater in cold weather may compromise longevity, contribute to excessive engine wear, and possibly damage engine. The engine block heater can be plugged in longer than listed in the schedule above without any negative effects or concerns, i.e. being left plugged in overnight.