6.5L GM Diesel Maintenance Schedule & Service Information

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	Notes
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	N/A
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
Serpentine Belt:	w/ AC, w/o vac pump	ACDelco 6K1010
Alternator:	1992 - 1995 (new, not reman)	ACDelco 3351015
Alternator:	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 NO PMD	ACDelco 212-367 Airtex 1R1332
Glow Plug Controller:	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
Fuel Lift Pump:	1994+	ACDelco EP309
Thermostat:	1992 - 1996 (195° F)	ACDelco 12T45E
Thermostat:	1997 - 2000 (195° F)	ACDelco 12T92E
Thermostat Housing Gasket:	ACDelco 12G11
Temperature Sender/Sensor:	Gauge temp sensor, all years	ACDelco 15-51107
Temperature Sender/Sensor:	ECM temp sensor, 1994 - 2000	ACDelco 213-4396
Upper Radiator Hose:	1992 - 1995	ACDelco 26171X
Upper Radiator Hose:	1996 - 2000	ACDelco 26318X
Lower Radiator Hose:	1992 - 1993	ACDelco 24231L
Lower Radiator Hose:	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

Component(s)	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	SAE 30W
	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)
Engine coolant ^[3]	1996+ model years	50/50 GM DEX-COOL, distilled water ACDelco 10-5027 (pre-mixed solution) ACDelco 10-101 (concentrate)	5.5 - 6.6 gallons (varies, refer to owners manual)
Automatic transmission fluid	GM 4L60E/4L65E, 4L70E, 4L80E/4L85E	ACDelco DEXRON VI ^[4]	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	ACDelco DEXRON VI ^[4] 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
Front differential	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.