Detroit Opens September Orders for Gen 6 EPA 2027 Truck Engines

Detroit will begin accepting orders September 1 for its Gen 6 DD13 and DD15 heavy-duty engines in Freightliner and Western Star trucks. Heavy Duty Trucking reported August 27 that the updated platform is designed for model-year 2027 federal emissions requirements while retaining about 75% of the prior generation's core components.

The design changes concentrate on fuel delivery, thermal management and aftertreatment. Detroit added a pre-selective-catalytic-reduction system and uses exhaust heat to bring emissions equipment to operating temperature faster. The company says the approach should reduce parked regenerations and can deliver roughly a 3% driving fuel-efficiency improvement for a typical linehaul fleet when thermal management and idle discipline are handled properly.

Detroit reports three years and more than 8 million miles of validation, including high-altitude, extreme-temperature and extended-idle testing. The aftertreatment package is intended to fit within existing chassis space, which may help vocational body builders avoid redesigning established upfits. The engines will be available for on-highway and vocational configurations offered through the two truck brands.

EPA's official July proposal would keep the 2027 nitrogen-oxide standard while modifying certain warranty, useful-life and DEF-inducement provisions, but it remains a proposal until finalized. Fleet buyers should separate manufacturer projections from guaranteed operating results and confirm the final certified configuration, warranty, maintenance intervals and DEF expectations before ordering. Driver training should also cover any revised regeneration indicators, diagnostic messages and shutdown procedures. The order opening signals that 2027 equipment planning is moving from policy discussion into procurement decisions.