[pciley]

I believe in frequent oil changes. Just to argue though, the service manual has good recommendations, but there is no oil change meter to throw a code for any technician to see. If you come in for service with 50,000 miles on the truck and all that comes out of the drain plug is 2 quarts of Log Cabin-looking maple syrup oil with chunks of rings and top end bearings floating around, they will know you haven't kept up the maintenance schedule. If you go 5000 miles on M1 or Amsoil you are doing your engine a good favor and your service dept. will be none the wiser that you are treating your truck so well yet going over 3500 miles between changes. BTW, i think theres a more loose maintenance schedule, like every 7500 miles. Would NOT recommend using that schedule with natural oils and average to heavy use.