On the CAT C7 the first oil/filter change should be done at 5 to 6,000 miles and then every 11,000 miles or 1 year according to CAT and Freightliner.
Here is a link to the Freightliner "Know Your Chassis" that you can download. It is an Adobe reader file. It has a lot of maintenance information about the Freightliner XC Chassis maintenance recommendations.
http://www.freightlinerchassis.com/mhMa ... ge=chassis
Ron