6.5 Diesel Maintenance Schedule

Applicable Models:

1992 - 2002 Chevrolet & GMC C/K series trucks, Suburban, C3500HD, etc

Applicable Engine(s):

6.5L GM diesel (turbocharged and naturally aspirated)

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 or in a manner that prevents the engine from reaching normal operating temperature (particularly important in cold 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.

6.5L Diesel Service Part Numbers

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.

Part Description

Part Number

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

ACDelco 212-367
Airtex 1R1332

1994+ MY w/ electronic injection, PMD

ACDelco 212-366
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

6.5L GM Diesel Fluid Specifications & Capacities


Oil/Fluid Specification

Capacity [1]

Engine oil [2]

Ambient temp > 0° F

SAE 15W-40 (preferred)
Recommend Amsoil Heavy Duty 15W-40 diesel oil

7 quarts w/ filter change (1992 - 1998 model year)

8 quarts w/ filter change (1999+ model year)

Ambient temp > 32° F


Ambient temp < 32° F

SAE 10W-30
Recommend Amsoil Heavy Duty 10W-30 diesel oil

Engine coolant [3]

1992 - 1995 model years

50/50 ethylene glycol engine coolant, distilled water
ACDelco 10-5015 (concentrate)

5.5 - 6.6 gallons
(varies, refer to owners manual)

1996+ model years

50/50 GM DEX-COOL, distilled water
ACDelco 10-5027 (pre-mixed solution)
ACDelco 10-101 (concentrate)

Automatic transmission fluid

GM 4L60E/4L65E, 4L70E, 4L80E/4L85E


11.5 - 13.5 quarts total capacity

Manual transmission fluid

New Venture NV4500

75W-90 Castrol Syntorq LT or equivalent specification [5]
MOPAR 4874459
GM 12346190
Recommend Amsoil 75W-90 manual transmission fluid

4 quarts

Hydraulic clutch fluid

GM 12345347


Transfer case fluid

New Process NP231, NP233

Recommend Amsoil OE Synthetic ATF

1.25 quarts

New Process NP241

2.3 quarts

BorgWarner BW4401, BW4472

1.5 quarts

BorgWarner BW4470

3.3 quarts

Front differential

AAM 8.25

75W-90 or 80W-90 GL-5 gear oil
Recommend Amsoil Severe Gear 80W-90 synthetic gear oil

1.51 quarts

AAM 9.25

1.82 quarts

Rear Differential

GM 8.6 (10 bolt)

80W-90 GL-5 gear oil
Recommend Amsoil Severe Gear 80W-90 synthetic gear oil

2.1 quarts

GM 9.5 (14 bolt, semi-float)

2.7 quarts

GM 10.5 (14 bolt, full float)

3.25 quarts

Dana 80 (C3500HD only)

75W-140 synthetic gear oil [6]
Recommend Amsoil Severe Gear 75W-140 synthetic gear oil

4.2 quarts

[1] Oil/fluid capacities are nominal - always fill to proper dipstick, fill plug, or indicator level. Fluid level should always be verified before and after driving vehicle.
[2] Engine block heater required in ambient temperatures below 0° F. GM recommends block heater operated minimum 8 hours before starting; use 10W-30 in such conditions.
[3] Recommend a quality extended life engine coolant (ELC) for all applications. DEX-COOL engine coolant has been the source of many cooling system problems. ELCs typically have a long service life with minimal required maintenance. Recommend Fleetguard CC2820 ELC (blue, 150,000+ mile service life, use with SCA/DCA Fleetguard DCA4) or Fleetguard CC36073 ELC (red, silicate free, 300,000+ mile service life).
[4] DEXRON VI supersedes original DEXRON II E and later automatic transmission fluid specifications. Transmission fluid capacity can vary considerably depending on model, options, and drive type (4 wheel drive vs. 2 wheel drive). Service capacity will be much lower than listed dry fill capacity.
[5] New Venture NV4500 transmission fluid specification is very specific and synchronizer damage will occur if one of the listed fluids is not used.
[6] C3500HD calls for 80W-90 GL-5 gear oil and 3,000 mile service intervals, OR 75W-140 full synthetic gear oil and 30,000 mile service intervals. Recommend full synthetic 75W-140 gear oil.