6.5L GM Diesel Maintenance Schedule

6.5L Diesel Maintenance Intervals & Service Information

GM's 6.5L V-8 diesel, designed and manufactured by the company's Detroit Diesel division, was introduced for the 1992 model year and represents an evolution of the original 6.2L Detroit platform. The engine is found in C/K series Chevrolet and GMC pickups through the 2000 model year in addition to several fullsize GM SUVs and various military applications. The engine was also used in the C3500HD chassis cab truck through the 2002 model year. As is the case for any vehicle, proper maintenance is critical maximizing the dependability and longevity of the 6.5L diesel.

Severe service conditions apply to vehicles that are:

• Driven in dusty environments
• Frequently used to tow a trailer or haul material
• Idled for extensive periods
• Frequently driven in stop-and-go traffic
• Frequently driven for short trips (5 to 10 mile distances, particularly important in below freezing weather)

6.5L GM Diesel maintenance schedule

Service Procedure

Recommended Interval


Replace air filter

Inspect at every oil change and replace as necessary. Replace regardless @ 15,000 miles under severe service conditions. Replace regardless @ 30,000 miles under normal service conditions.

Part number(s) available in service part/specs below.

Change engine oil, replace oil filter

Change engine oil and replace oil filter every 2,500 miles under severe service conditions, 5,000 miles under normal service conditions.

7 quart capacity w/ filter through 1998 model year, 8 qts w/ filter capacity 1999+ model years.

Replace fuel filter

Replace fuel filter every 30,000 miles.

GM recommends 30,000 mile fuel filter replacement intervals. However, more frequent fuel filter service is advised - consider replacing every other oil change, especially on older vehicles.

Replace serpentine belt

Inspect serpentine belt every oil change and replace as necessary.

Replace belt when grooves are worn, belt begins to squeal, or belt exhibits cracking.

Change automatic transmission fluid

Replace transmission fluid and filter every 50,000 miles

Capacity varies with application - refer to owners manual or fill to correct operating range per dipstick indicator.

Change manual transmission fluid

50,000 to 100,000 mile fluid replacement advised depending on conditions; frequent towing should result in more periodic service

GM suggests the NV4500 manual transmission does not require service and is "filled for life". We recommend servicing the transmission periodically to maximize synchronizer life. Follow GM fluid spec - failure to use a compatible fluid will result in premature transmission damage.

Change front differential fluid

Replace differential fluid at 15,000 mile intervals

General Motors 9.25" IFS differential, 1.83 qts fluid capacity

Change rear differential fluid

Replace differential fluid at 15,000 mile intervals, check fluid level at every oil change and add as necessary

Capacity varies, always fill differential to fill plug level - see fluid spec breakdown below. More frequent differential service may be required on C3500HD chassis cab trucks with a Dana 80 axle. An additive may be required in limited slip differentials - refer to owners manual.

Cooling system service

Flush cooling system, replace upper/lower radiator hose and thermostat every 30,000 miles or 24 months

Capacity varies by application and model year - refer to owners manual.

Replace glow plugs

Replace glow plugs and glow plug controller every 100,000 miles


Replace CDR valve

Replace CDR valve every 60,000 miles

Replace CDR valve hose if damaged, excessively soaked in engine oil, or is otherwise worn.

Replace Harmonic Balancer:

Replace harmonic balancer every 100,000 miles

Harmonic balancers known to fail after 100,000 miles. Replacement interval is not a GM recommendation, but due to the frequency of failures it is the general consensus, not just our recommendation, to replace the harmonic balancer at 100,000 mile intervals.


Common Service Part Numbers & Fluid Specifications

Service parts and part numbers applicable to C/K pickups and select chassis cab trucks - part numbers may vary for alternative 6.5L diesel applications. Always verify part fitment with your parts retailer. Click on a p/n for pricing and additional information.

Engine Air Filter:

1992 - 1996

WIX 46316

1997 - 2000 w/o out high cap. filter

ACDelco A1300C

1997 - 2000 w/ high cap. filter

ACDelco A1301C

Engine Oil Filter:

ACDelco PF1218

Fuel Filter:

ACDelco TP1256F

Fuel Filter Strainer:

Stanadyne/Clarcor 29244

Fuel Filter Retainer Ring/Nut:

ACDelco 12511963

Fuel Tank Strainer/Sock:

ACDelco TS1012(in-tank sending unit filter)

Serpentine Belt:

w/ vac pump & AC

ACDelco 6K1020

w/ AC, w/o vac pump

ACDelco 6K1010


1992 - 1995 (new, not reman)

ACDelco 3351015

1996 - 2000 (new, not reman)

ACDelco 331068

Starter Motor Assembly:

ACDelco 3371002 (new, not reman)

Glow Plug:

ACDelco 60G

Glow Plug Controller:

All 1992 - 1993 MY
1994+ MY w/ mechanical injection pump

Airtex 1R1332

1994+ MY w/ electronic injection, PMD

Airtex 1R1372

CDR Valve:

ACDelco CV916

CDR Valve Hose/Elbow:

ACDelco 10154603

Oil Pressure Sensor/Switch:

ACDelco D1808A

Fuel Lift Pump:

1992 - 1993

ACDelco EP158


ACDelco EP309


1992 - 1996 (195° F)

ACDelco 12T45E

1997 - 2000 (195° F)

ACDelco 12T92E

Thermostat Housing Gasket:

ACDelco 12G11

Temperature Sender/Sensor:

Gauge temp sensor, all years

ACDelco 15-51107

ECM temp sensor, 1994 - 2000

ACDelco 213-4396

Upper Radiator Hose:

1992 - 1995

ACDelco 26171X

1996 - 2000

ACDelco 26318X

Lower Radiator Hose:

1992 - 1993

ACDelco 24231L

1995 - 2000

ACDelco 26264X

Radiator Cap:

ACDelco 12R7 or ACDelco 12R7S (w/ safety relief)

Rear Differential Gasket:

GM 14 bolt

Dana Spicer RD51995

Dana 70

Dana Spicer RD51998

Dana 80 (3500HD models)

Dana Spicer RD51997

PTO Cover Gasket:

Mahle/Victor-Reinz H26206, 0.020" thick, 6 bolt cover (NV4500 man. trans)
Mahle/Victor-Reinz H26205, 0.010" thick, 6 bolt cover (NV4500 man. trans)

Engine Oil:

SAE 15W-40 preferred, temp > 0° F
SAE 30W acceptable, temp > 32° F
SAE 10W-30 acceptable, temp < 32° F

Automatic Transmission Fluid:





Manual Transmission Fluid:

Castrol Syntorq LT, ACDelco 12346191 (NV4500 5 spd trans)

Hydraulic Clutch Fluid:

GM 12345347

Engine Coolant:

1992 - 1995 MY

ACDelco nitrited diesel ELC

1996+ MY

ACDelco Dex-Cool engine coolant

Front Differential Fluid:

SAE 75W-90 full synthetic gear oil

Rear Differential Fluid:

GM 14 bolt, Dana 70

SAE 80W-90 GL-5

Dana 80 (3500HD models)

SAE 75W-140