Cummins PX-9 345EV

Although it carries the PACCAR nameplate, the engine is actually manufactured by Cummins: in 2006 the two companies agreed that Cummins would build the 6- and 8-liter engines exclusively for Kenworth and Peterbilt, badged as PACCAR units. The PX-9 shares its basic block with the Cummins ISC/ISL but uses a longer stroke to reach its larger displacement.

It is fitted mainly to the Kenworth T270, T370, T440, T470 and the W900S — vocational and regional-haul trucks where maneuverability and payload matter more than maximum highway range.

Like other US highway diesels in this class, the PX-9 meets the strict North American NOx limit in force since 2010 only with a combination of cooled exhaust-gas recirculation, a diesel particulate filter and an SCR catalyst with AdBlue dosing. Injection is handled by a high-pressure common-rail system, which replaced the mechanical inline injection pump used on older Cummins engines; like the related ISC/ISL units, the inline six runs on wet cylinder liners that can be replaced individually during a major overhaul. In distribution and vocational work, a strong torque curve at low engine speed matters more than a high rated speed.

On used units, check for a complete emissions-system service record (EGR/SCR), since engines of this class in the US highway segment are known to be sensitive to neglected oil-change and filter intervals.