Detroit Opens Orders for Gen 6 DD13 and DD15: EPA 2027 Engines Go From Announcement to Order Banks
Detroit has put a date on the EPA 2027 transition. Daimler Truck North America announced on August 26, 2026 that customers can begin specifying the Detroit Gen 6 DD13 and DD15, the EPA 2027-compliant engines that will power Freightliner and Western Star trucks, with ordering opening September 1. Production starts in January 2027, with the Gen 6 DD16 following in January 2028. For buyers planning 2027 equipment, the order banks opening marks the point where the EPA 2027 transition moves from press releases to actual spec sheets.
What happened
Customers can specify the Gen 6 DD13 and DD15 in both Freightliner and Western Star heavy-duty models. Detroit, DTNA's powertrain brand, positions the lineup as an evolution rather than a clean-sheet redesign: approximately 75% of Gen 6 core components carry over from the previous generation, preserving the durability, serviceability, and operating characteristics fleets already know.
"Customers don't want to choose between proven performance and future-ready technology. With the Detroit Gen 6 engine platform, they don't have to," said David Carson, senior vice president of sales and marketing at Daimler Truck North America.
The DD platform behind these engines launched in 2007 and has passed 1.2 million engines sold in on-highway and vocational applications. Gen 6 is the first update built for the EPA's 2027 rule, which cuts the heavy-duty NOx limit to 0.035 g/bhp-hr from the current 0.2 g/bhp-hr. Detroit says the platform completed three years of testing in extreme temperatures, high-altitude conditions, and extended idling, plus more than 8 million miles of real-world validation.
| Engine | Displacement | Power Ratings | Torque | Production Start |
|---|---|---|---|---|
| Gen 6 DD13 | 12.8 L | 410-525 hp | 1,450-1,850 lb-ft | January 2027 |
| Gen 6 DD15 | 14.8 L | 425-505 hp | 1,550-1,900 lb-ft | January 2027 |
| Gen 6 DD16 | 15.6 L | 560-605 hp | 1,850-2,050 lb-ft | January 2028 |
The technology behind the compliance
Gen 6 meets the 2027 NOx limit with a pre-SCR (light-off SCR) unit positioned upstream of the primary aftertreatment system, paired with a thermal control valve that uses exhaust heat to bring the aftertreatment up to operating temperature faster. The practical result Detroit cites: fewer parked regenerations. The one-box aftertreatment keeps the same frame-rail space as today, so vocational body builders do not need to redesign upfits.
On the engine side, a simplified high-pressure common-rail fuel system with an oil-lubricated injection pump removes the need for amplified injectors. Miller-cycle cam timing, an asymmetric intake port, and new injectors improve combustion efficiency. One detail worth noting for anyone who maintains these trucks: the Gen 6 uses an asymmetric turbocharger with a wastegate valve to control boost pressure across a wider operating range, which also supports engine braking and holds heat for regenerations. It is a different turbo specification from the units on today's DD13 and DD15, and correct identification will matter when these trucks enter the aftermarket.
What it means for fleets and the aftermarket
- Order timing is now a real decision. With order banks opening September 1 and production starting in January 2027, fleets wanting early Gen 6 builds need to prepare specs now; fleets holding current-generation trucks face no forced change, since 75% carryover keeps the service experience familiar either way.
- Vocational upfits carry over unchanged. The aftertreatment system fits existing chassis space with no back-of-cab impact, so body builders and equipment installers can keep current designs.
- Fewer parked regens change daily operations. Faster aftertreatment warm-up targets one of the most common driver complaints on current emissions hardware.
- New hardware variants are coming to the parts market. The asymmetric wastegated turbocharger and pre-SCR aftertreatment are Gen 6-specific. As these engines age into the repair cycle, matching parts by engine serial number rather than by engine name will separate a correct repair from a comeback.
Where this touches our business
Every new engine generation eventually becomes an aftermarket parts question. UPAPSI supplies brand-new, never-remanufactured turbochargers for the diesel engines fleets run today, including Detroit turbocharger applications across the DD series, stocked in our US warehouse with a one-year unlimited-mileage warranty and no core charge. Whether you are maintaining current DD13 and DD15 units or planning for Gen 6, send us the engine serial number and we will confirm the correct turbo for the application.
Sources
- Modern Public Fleet: "Detroit Opens Ordering for Gen 6 DD13 and DD15 Engines in Freightliner and Western Star Trucks" (August 26, 2026)
- DieselNet: "Daimler announces EPA 2027 compliant Detroit engines" (February 23, 2026)
- Transport Topics: "Detroit Launches Next Generation of DD-Series Engines" (February 19, 2026)
