I was told by the dealer fleet sales rep to change it at 7500 miles, I haven't done that ever. I was trying to change the oil and filter around 3500 miles. I've heard the oil will quit getting dirty right away after changing once the motor gets broken, between 35,000 to 60,000 miles, mine hasn't done that yet at 151,000+ miles I'm going to try changing it around 5,000 miles now for a while and see if I like that or not Thanks for the help to all of you
Nature of the beast Cab. Some are worse than others. My Cat stays fairly clean looking right up to 12,000 miles. My N14 Cummins was black by the end of the driveway. I think ring design and better filtering on the Cat account for most of the difference.
Cummins filter specs are considerably more lax than Cat. A Cummins N14 fuel filter is 10 micron. A Cat is 3.
