[skillet]

I have the same year suburban with oil cooler. The Chilton's manual(1988-96) says, "If the engine is equipped with an oil cooler, this will also have to be drained, using the drain plug. Be sure to add enough oil to fill the cooler in addition to the engine." I assume they're talking about the oil pan drain plug. I've never added any extra oil though, just the normal 5 quarts. But, you're question makes me wonder if I have been doing it right. I bought it with 114K and it now has 163K. At least it has seemed to have worked for the last 49K miles with no problems and it still runs great, even after a trip to Utah over some pretty steep mountains and back to Texas.