The oil was changed at miles 4006, 8574, and 13203, with MC semi-syn 5-30...not real happy with a TBN of 2.0 with only 4629 miles on this oil....truck was driven normal, with some towing of approx. 1000 miles(load of about 2500lbs.)...Oil life monitor claimed 49% at 4629, can't see going much more than 5000 miles!....The truck has officialy been owned 1 year....computer says 470hours18minutes, 867.8 gallons of fuel used, 13,480 miles, and 15.5 mpg.average....The truck towed for approx. 3000 of those miles, took about 2000 miles of highway driving, and the rest was city/rural mix...I also think the computer is conservative on calculating mpg, typcally the computer would say the truck used .1 to .2 gallons more fuel, than could actually be topped off with...