| Engine oil & filter | SAE 5W-30 meeting GM6094M · 6.0 qt (5.7 L) with filter | When the oil-life monitor says so, and at least once a year | The 2004 manual lists the ACDelco PF44 filter (GM 25010633). The 2008 manual lists the PF48 (GM 89017524).Oil filter (catalog, 2005 H2) · RockAuto ↗Oil filter (catalog, 2008 H2) · RockAuto ↗ |
| Engine air filter & cabin filter | GM 88944151 (2004 manual) · ACDelco A2948C / GM 10389652 (2008 manual) | Inspect at every oil change; replace per the manual's schedule | Dusty trails clog it quickly. Check it after any desert trip.Air filter (catalog, 2005 H2) · RockAuto ↗Cabin air filter (catalog, 2005 H2) · RockAuto ↗ |
| Spark plugs & wires | ACDelco 41-985 (GM 12571164) · gap 0.040 in (1.01 mm) | Per the owner's manual schedule confirm in manual; do them now if there are no receipts | The same plug is listed for the 6.0 and the 6.2. Inspect the wires when you change the plugs, as the manual says.Spark plugs (catalog, 2005 H2) · RockAuto ↗Spark plug wires (catalog, 2005 H2) · RockAuto ↗ |
| Coolant | DEX-COOL 50/50 · 13.0 qt (2004 manual); 16.7 qt SUV / 15.4 qt SUT (2008 manual) | 5 years or 150,000 mi, whichever first | The manual warns that other coolants can corrode the radiator and heater core. One forum owner changes it every three years to protect the aluminum.Coolant (catalog, 2005 H2) · RockAuto ↗Thermostat (catalog, 2005 H2) · RockAuto ↗ |
| Automatic transmission fluid & filter | DEXRON-III (4L65-E, 2003–07) · DEXRON-VI (6L80, 2008–09) · 6.0 qt with pan removal and filter (2008 manual) | Fluid and filter on the severe-service schedule if you tow, run hills or sit in hot traffic | Do a pan drop and filter change rather than a flush. Owners call the four-speed the weak link, so treat its fluid as cheap insurance.Transmission filter (catalog, 2005 H2) · RockAuto ↗Transmission fluid (catalog, 2008 H2) · RockAuto ↗ |
| Transfer case (BW 44-84) | DEXRON-III (2004 manual) · DEXRON-VI (2008 manual) · 1.5 qt (1.4 L) | Per the manual's mileage schedule; more often if you wade or tow | Fill to just below the fill hole. The manual also says to check that the transfer-case vent hose isn't kinked. Loosen the fill plug before you open the drain.Transfer case fluid (catalog, 2005 H2) · RockAuto ↗Transfer case vent (catalog, 2005 H2) · RockAuto ↗ |
| Front & rear differentials | SAE 75W-90 synthetic meeting GM 9986115 (GM 12378261 in the 2004 manual, 89021677 in 2008) | At purchase, then after any deep water crossing | Owners report the front takes about 2 quarts and the rear about 3. Many run Mobil 1 75W-90 synthetic. A forum owner warns that conventional 85W-90 can make the front diff stick and dart on cold mornings.Gear oil (catalog, 2005 H2) · RockAuto ↗Differential cover gasket (catalog, 2005 H2) · RockAuto ↗ |
| Chassis grease | NLGI #2 chassis lubricant (GM 12377985) | At every oil change | Grease the front suspension, ball joints and steering linkage, but not the ball joints below 10°F (-12°C), per the manual. Dealers don't always do it: one was told the joints were sealed. The front propshaft spline takes GM spline lubricant 12345879.Idler arm grease hose (catalog, 2005 H2) · RockAuto ↗ |
| Power steering fluid | GM power steering fluid 89021184 | Check at every oil change; flush if dark | The H2 uses Hydro-boost brakes, so the power steering pump also powers the brake booster. NHTSA's 05V455000 recall notes that losing steering fluid can also mean losing power brakes.Power steering fluid (catalog, 2005 H2) · RockAuto ↗ |
| Brake fluid | DOT 3 (Delco Supreme 11 or equivalent) | Flush at purchase if there's no record | A 6,400-pound truck on big tires needs good brakes. Car and Driver measured 244 ft from 70 mph on a stock 2003.Brake fluid (catalog, 2005 H2) · RockAuto ↗ |
| Fuel filter | ACDelco GF626 (GM 25121792) in the 2004 manual's parts list | At purchase if there's no record confirm in manual | The 2008 manual's maintenance parts list doesn't include a separate fuel filter, so check whether your year has one.Fuel filter (catalog, 2005 H2) · RockAuto ↗ |
| Drive belt & hoses | Serpentine belt; inspect the cooling hoses | Inspect per the manual's schedule; replace when cracked | The manual recommends a yearly pressure test of the cooling system and cap.Serpentine belt (catalog, 2005 H2) · RockAuto ↗ |
| Rear air suspension (if fitted) | Compressor, two height sensors, two air springs | Check at purchase | Listen for the compressor running constantly and look for a rear that sags overnight, both signs of a leak. The owner's manual says leveling stops with any door open.Ride height sensor (catalog, 2005 H2) · RockAuto ↗ |
| Battery | Group 79 stock, according to owners | Test at purchase | A weak battery causes odd 4WD and electrical faults, and the rear locker disengages when battery voltage is low (owner's manual). Owners say other group sizes fit if you leave out the plastic battery box. |