Reasonably low original miles on the odometer at only 217k, the best drivetrain that was available from GMC Commercial Trucks is in this truck, a CAT designed and built, INLINE 6 CYLINDER, 7.2 LITER, turbo diesel engine hooked to a Allison 5 speed automatic overdrive transmission. there is no diesel soot particulate filter to need 15 to 30 minute at a time multiple daily manual regenerations, nor does it have a DEF (Diesel Emission Fluid) tank that takes time and bottom line cash to fill. It is fuel efficient and reliable because of what it doesn't have Tachometer