I've heard various suggestions as to oil change intervals on the 6.0. Mine is a '06 in an F250 automatic. Though I do have a heavy 5er that I tow from time to time (not too many miles each year) most of my driving is around town to and from work unloaded. Phoenix AZ can be quite dusty so that might also change the suggestions. Just curious if there is something that is more objective as to the interval between changes.