1994 GMC Suburban Owner's Manual - Page 262

Engine Oil (Except Diesel) It's a good idea to check your engine oilevery time you get fuel. In order to get an accurate reading, the oilmust be warm and vehicle must be on the level ground. Turn off the engine and give the oil a few minutes to drain back into the oil pan. If you don't, the oil dipstick might not show the actual level. e To Check EngineOil h l l out thedipstick and clean it with a paper towel or cloth, then push it back in all the way. Remove it again, keeping the tip lower. When to Add Oil If the oil is at below the ADD mark, then you'll need to addsome oil. But or you must use the right kind. This section explains what kind of oil to use. For crankcase capacity, see "Capacities and Specifications" in the Index.