I was using what was recommended for the Tahoe, but I have an '01 and it's been burning through the recommended oil so I went with Royal Purple 10W30. Oil has been hasn't been burning off like it was before. I had an oil change done at Pepboys which I shouldn't have, and the within the first month of DIC said Low Oil. I checked and the oil was really low. I put in a couple of quarts Royal Purple 10W30 and it's been great. I need to do a full oil change myself and change the oil filter to RP also. I might do that soon if it doesn't snow.