Cary,
I'm using Mobil 1 0W40 as recommended to me. Last change was maybe 2500 miles ago and done just before CM07 so less than 3 months ago. Will be changing the oil in the next few weeks despite many stating with synthetics you can go longer. My aftermarket warranty requires that I follow the 3 month/3000 mile rule so no biggie.
What is wierd is that I've owned the rig since last November and have never heard it make this noise before. First time I heard it was about 10 days ago on startup at a house up in Grand Lake CO (~8500') while on vacation. Seems wierd that I'm hearing it now![]()
I'm guessing it is something else besides startup rattle. Given your intervals, I would suggest you consider going to the Rotella or Chevron Delo 15w-40 summer, and 5w-30 in the winter. There is no point running a synthetic for the short intervals, you are just spending unnecessary money.