I am thinking about changing my 99 Saturn SL over to Mobil 1 0-40. It currently is using Mobil 1 10-30. I have been using a 5k mile interval. Last winter I used 5-30. I would like to change to the Mobil 1 0-40 year round and go with a 6K mile change interval. Any thoughts? Next- 2000 Silverado with a 5.3- Currently using Mobil 1 10-30 also with 5k intervals. Last winter I used Mobil 1 0-30. I would like to switch back to that due to some more start up noise that I am hearing with the 10-30. This last interval my change oil light came on at about 4800 miles. This was the first time that I has come on and yes I do reset it every oil change. Napa Gold oil filters for both!! Both burn/use about between 1/2 and 3/4 of a quart for the entire interval. Thanks guys!!!