Oil change interval

[TorresTransport]

I'm going from driving in the city to regional diving my question is how often to I change my oil? In the city I change it every 8000 miles with 15w40 Rotella do I stick with that or stretch it out a lot longer to say 12000 or 14000 with the same oil??

[j hancock]

Mack "Line Haul" recommendations from a few years earlier (1995) was for oil and filters at 25,000 miles or 600 hours, whichever came first.  Mack "Short Haul" spec was for oil and filters at 600 hours.