1998 GMC Sonoma Owner's Manual - Page 275

When the differential is cold, add enough lubricant to raise the level to 1/2 inch (12 mm) below the filler plug hole. When the differential is at operating temperature (warm), add enough lubricant to raise the level to the bottom of the filler plug hole. What toUse Refer to the Maintenance Schedule to determine what kind of lubricant to use. See "Recommended Fluids and Lubricants" in the Index. A SO/SO mixture of water and DEX-COOL@ coolant will: Give freezing protection down to -34°F (-37°C). Give boiling protection up to 265°F ( 1 29°C). Protect against rust and corrosion. Help keep the proper engine temperature. Let the warning lights and gages work as they should. Engine Coolant The cooling s stem in your vehicle is filled with DEX-COOL J engine coolant. This coolant is designed to remain in your vehicle for 5 years or 150,000 miles (240 000 km) whichever occurs first, if you add only DEX-COOL6 extended life coolant. The following explainsyour cooling system and how to add coolant when it is low. I f you have a problem with engine overheating, see "Engine Overheating" i n the Index. I NOTICE: When adding coolant, it important thatyou use is only DEX-COOL@ (silicate-free) coolant. If coolant other than DEX-COOL added to the is system, premature engine, heater core or radiator corrosion may result. In addition, the engine coolantwill require change sooner at 30,000 miles (50 000 km) or 24 months, whichever occurs first. Damage caused the use by of coolant other than DEX-COOL@ not is covered by your new vehicle warranty. -- 6-25