GENECARP, I would suggest following what volvoman says. If you don't drive 8,000 miles a year, I suggest twice a year do an oil & filter change, on one of the visits- do fuel filters, chassis and driveline lube, and don't forget the coolant checks, brake adjusters, etc. During your travels you will see J-Lube, Speedco, Petrolube or other quick lubes at the truck stops. Stop by and see their schedule of services and talk to one of the techs and you may get a better understanding of a full service or a minor oil change.
Just my two cents.
'18 Renegade 45'
Volvo Twin Screw, 500 hp I-Shift 12 Speed
30' Renegade Stacker Trailer