Daimler Opens Detroit Gen 6 Order Book Sept. 1 for 2027 NOx Rule
Freightliner and Western Star dealers start taking orders for EPA 2027-compliant engines next week. What the new NOx hardware costs and when trucks ship.
When can fleets order Detroit Gen 6 engines?
Daimler Truck North America will open the order book for Detroit Generation 6 engines September 1, 2026. The Gen 6 engines meet Environmental Protection Agency 2027 nitrogen oxide emissions rules that take effect January 1, 2027.
Freightliner and Western Star dealers will begin taking orders for trucks equipped with the new powertrains next week. DTNA has not disclosed pricing for the Gen 6 engines or the upcharge versus current-generation Detroit DD13 and DD15 models.
What changes in the Gen 6 aftertreatment hardware
The EPA 2027 NOx rule cuts the allowable nitrogen oxide emissions limit to 0.02 grams per brake horsepower-hour, down from the 0.20 g/bhp-hr standard that has been in place since 2010. Meeting the new standard requires changes to the selective catalytic reduction system, diesel oxidation catalyst, and diesel particulate filter.
DTNA has not released detailed specifications for the Gen 6 aftertreatment package. The company has not disclosed whether the new hardware adds weight, changes service intervals, or requires different diesel exhaust fluid consumption rates compared to current Detroit engines.
When Gen 6 trucks start shipping
Trucks equipped with Detroit Gen 6 engines must ship by January 1, 2027, when the EPA 2027 NOx rule becomes mandatory for new production. DTNA has not announced whether it will begin delivering Gen 6-equipped trucks before the regulatory deadline or hold shipments until January.
Fleets ordering current-generation Detroit engines after September 1 will need to confirm with dealers whether those orders can still be filled with pre-2027 powertrains or whether all new orders will default to Gen 6 hardware.
What the Gen 6 order timeline means for small fleets
Small fleets planning 2027 truck purchases face a decision point in the next four months. Ordering current-generation Detroit engines before January 1 may lock in lower upfront cost if Gen 6 hardware carries a premium, but it also means buying a truck that will be one emissions generation behind within weeks of delivery.
Fleets that wait for Gen 6 trucks will get hardware designed for the tighter NOx standard, but they will also be early adopters of a new aftertreatment system with no field service history. The Gen 6 engines will carry Detroit's standard warranty, but DTNA has not disclosed whether warranty terms or coverage will change for the 2027-compliant hardware.
Fleets should ask dealers for Gen 6 pricing, weight specifications, DEF consumption estimates, and service-interval details before committing to orders. DTNA has not released that data publicly as of August 28, 2026.
