1994 GMC Sonoma Owner's Manual - Page 241

If the differential is at operating temperature (warm), add enough lubricant to raisethe level to the bottom of the filler plug hole. If the differential is cold,add enough lubricant to raise the level to 1/2 inch (12 mm) below the filler plug hole. What to use Refer to theMaintenance Schedule to determine what kind of lubricant to use. See "Recommended Fluids and Lubricants" in the Index. Engine Coolant The following explains your cooling system and how to add coolant when it is low. If you have a problem with engine overheating, see "Engine Overheating" in the Index. The proper coolant for your vehicle will: Give freezing protection down to -20 " F (-29"C), or -34°F (-37 "C) in Canada and for vehicleswith the cold climate option. 0 Give boiling protection up to 258"F ( 1 25 "C). Protect against rust and corrosion. Help keep the proper engine temperature. Let the warning lights and gages work as they should. 0 What to Use Use a mixtureof one-half clean water (preferably distilled) and one-half antifreeze that meets "GM Specification 6038-M" or "GM Specification 6043-M "for the 2.2L (LN2) Code 4 engine, which won't damage aluminum parts. You can also use a recycled coolant conforming to "GM Specification 6038-M" or "GM Specification 6043-M "for the 2.2L (LN2) Code 4 engine with a complete coolant flush and refill. If you use this mixture, you don't need to add anything else. 6-23