6.5L GM Diesel

6.5L Detroit Diesel Specs, History, & Information


The 6.5L GM diesel was introduced in 1992, replacing the 6.2L in 1993. Also manufactured by Detroit Diesel, the 6.5 was available in several versions to serve several different applications. The 6.5L, like the 6.2L, was underpowered in comparison to its competitors diesel options, but focused more on providing a fuel efficient alternative. A special "Fuel Miser" version of the 6.5 surfaced in P-trucks (delivery trucks for bread/snack food companies) that produced the fuel mileage of a four cylinder. The 6.5L was offered in naturally aspirated & turbocharged versions. It is still in use today by AM General in the HMMWV military vehicles.


6.5L GM Specs


Detroit Diesel (a division of GM at the time)

Production Years:

1992-2000. Currently still used in military applications, produced by AM General.


Chevrolet/GMC: Tahoe, Yukon, Suburban, C/K pickups, 2500 & 3500 trucks. AM General: Hummer & HMMWV



Block/Head Material:

cast iron block, cast iron heads


395 cubic inches, 6.5 L


18:1 - 21.3:1 depending on year & application


4.06 inches


3.82 inches


IDI (indirect injection)


Turbocharged & naturally asprirated versions available.

Max Engine Speed:

3,400 RPM


Introductory: 180 HP @ 3,400 RPM
Peak: 215 HP @ 3,200 RPM


Introductory: 360 HP @ 1,700 RPM
Peak: 440 lb-ft. @ 1,800 RPM


Outperformed by Dodge & Ford engines of the same period. Capable of respectable fuel economy. Somewhat problematic depending on version of engine.
























6.5L Detroit/GM Diesel Information

• Offered in naturally aspirated & turbocharged versions.

• The 6.5L was replaced by the Duramax 6600 (6.6 L).

• AM General now manufacturers and uses the 6.5 L diesel in their military HMMWV (now called the 6500 Optimizer).

• Common problems with the 6.5L included cracks in the main caps & crankshaft failures due to aging/fatigue of the harmonic balancer. Glow plugs are prone to failure (causes hard starting), overheating issues in the 1988-1998 style trucks (can lead to cracked cylinder heads).


6.5L GM Engine Versions

• L49: Naturally aspirated.

• L56: Turbocharged. Emissions controlled (EGR & catalytic converters). Used in all light duty 1/2 & 3/4 ton trucks.

• L57: Naturally Aspirated. HO or heavy duty.

• L65: Turbocharged. Used in all heavy duty 3/4 & 1 ton trucks.

• LQM: 175 HP

• LQN: 190 HP

• "Fuel Miser": 120 HP, 260 lb-ft. torque. Optional in P-trucks (delivery trucks).



Related Topics:

6.2L GM Diesel Specs

7.3L IDI Specs

5.7L Olds Diesel Specs

6.9L IDI Specs