The 1989 Suburban, available through GMC or Chevrolet, offered a 5.7L and a 7.4L eight-cylinder gasoline engine as well as a 6.2L diesel engine. Each engine type uses different levels but similar types of fluids. Manufacturer recommendations for fluid capacities and types include oil and transmission, differential and transfer cases, and hydraulic systems.
The gasoline engines require SAE 5w30 oils and the diesel calls for SAE 15w40 synthetic oil. All the vehicles call for synthetic multi-vehicle automatic transmission fluid (ATF) in the transmission. The 5.7L uses 4.1 quarts of engine oil without a filter change, while the 7.4L calls for 5.1 quarts. The diesel engine uses 7 quarts, which includes a filter change.
The transfer case, if equipped, uses standard ATF (synthetic) transmission fluid, and the differential calls for SAE 80w90 gear oil. All vehicles use the same fluids for the transfer case and differential. Capacities vary by type of differential or transfer case and engine size. Fill the cases through the fill hole (used to check the level of fluid near the top quarter of the transfer case or differential) until the fluid is flush with the center of the hole.
The hydraulic systems include brakes, clutch and power steering. Each system uses a reservoir with fill lines and requires bleeding if you change any parts. Use DOT-3 brake fluid for the brake and clutch reservoirs, and standard power steering fluid for the power steering on all vehicles. Fill to the fill line on the reservoir, but monitor closely when bleeding the various systems. Never let the level drop beneath half-full.
