haul freight ,expediter. about 8000 miles a month, heavy duty use of tires, oil, filters, and the like.
Dont have time for breakdowns, but it happens, engine runs sometime 15 hr days and idles a lot, mmo and rotella t6 I have faith in.  I do a pan drop on the tranny every 50k miles and filter. Plugs once a year, tires dont last long, im rough on tires and road hazzards seem to come my way.  the only engine additive I use is MMO now and I add it to the powersteering pump too.  I use lubegard red in the tranny and added a extra tranny cooler in front of the radiator and I do not run tranny thru the radiator anymore.  I use atf4 transmission fluid too.  I carry a portable generator and window unit airconditoner for the summer, microwave and coffee pot, dont have time for nonsense usually. Its a business out here.