Mack Trucks Unveils 2027-Compliant MP13 Engine at ACT Expo

Mack Trucks showed a production-intent MP13 engine that meets the EPA's 2027 nitrogen oxide emissions standard at the 2026 ACT Expo in Anaheim on May 5. The engine is the first Class 8 powerplant publicly unveiled with hardware designed to comply with the new rule, which cuts allowable NOx emissions by 75 percent from the current 0.20 grams per brake horsepower-hour to 0.05 g/bhp-hr.

What changes in the 2027 MP13 to meet the NOx rule?

Mack has not yet released detailed specifications on the aftertreatment hardware or calibration changes required to hit the 0.05 g/bhp-hr target. The company confirmed the engine displayed at ACT Expo is a production-intent design — meaning the architecture shown is what will ship in 2027 model-year trucks — but did not disclose whether the compliance strategy relies on revised SCR catalyst formulation, additional DEF dosing, a redesigned EGR cooler, or a combination of all three.

The MP13 is Mack's 13-liter inline-six, used across the Anthem and Pinnacle lineups. Current-generation MP13 engines are rated from 415 to 505 horsepower and 1,560 to 1,860 lb-ft of torque. Mack has not stated whether 2027-compliant versions will carry the same power and torque bands or whether meeting the NOx target requires derating.

When does the 2027 rule take effect?

The EPA's 2027 heavy-duty engine rule takes effect for model year 2027, which begins production in early calendar 2026 for most OEMs. Engines built after January 1, 2027 must meet the 0.05 g/bhp-hr NOx standard. The rule also tightens particulate matter limits and introduces a new low-load cycle test intended to capture emissions during urban stop-and-go operation, where current certification tests underrepresent real-world NOx output.

Mack's May 5 unveiling puts the MP13 ahead of most competitors in the public timeline. Cummins, PACCAR, and Navistar have all confirmed they are developing 2027-compliant engines but have not yet shown production hardware. Daimler Truck North America, Mack's sister company under the Volvo Group umbrella, has not announced a reveal date for its DD13 and DD15 engines.

What does 2027 compliance cost?

Mack has not released pricing for 2027 MP13 engines or the delta versus current-generation units. Industry estimates for the incremental cost of meeting the 2027 NOx rule range from $3,000 to $8,000 per truck, driven primarily by larger or more complex aftertreatment systems, additional sensors, and more frequent DEF consumption. The actual cost will depend on each OEM's compliance strategy — whether the solution is catalyst volume, dosing rate, thermal management, or a redesigned combustion chamber.

Fleets should also plan for higher DEF consumption. The 75 percent NOx reduction requires more selective catalytic reduction activity, which means more DEF per mile. Current Class 8 trucks consume roughly 2 to 3 percent of fuel volume in DEF; 2027 engines are expected to push that ratio closer to 4 to 5 percent, adding $0.01 to $0.02 per mile in fluid cost at current DEF prices.

What this means for fleets ordering 2027 trucks

Fleets placing orders for 2027 model-year trucks should confirm with their OEM whether the quoted price includes 2027-compliant engines or whether a price adjustment will follow once final hardware costs are locked. Most manufacturers are taking orders now but have not finalized 2027 engine pricing, leaving room for upward revision as production nears.

Shops should also prepare for new service procedures. The 2027 rule's low-load cycle test and tighter PM limits suggest more sensitive aftertreatment systems that may require more frequent regeneration monitoring, DEF quality checks, and NOx sensor replacement. Mack has not yet published service intervals or warranty terms for the 2027 MP13, but fleets can expect guidance closer to the start of production.

The MP13's early reveal gives Mack a head start in customer education and pre-production testing, but the lack of published specs — power, torque, fuel economy, service intervals, warranty coverage — means fleets cannot yet compare total cost of ownership against competitors. That data will determine whether the 2027 MP13 is a straight replacement for current engines or whether meeting the NOx target extracts a penalty in performance, fuel economy, or uptime.