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 |
| w/ AC, w/o vac pump | ACDelco 6K1010 | |
| Alternator | 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 NO PMD |
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 |
| 1994+ | ACDelco EP309 | |
| Thermostat | 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
| 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) |
| 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 | 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 |
| 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.