Kenworth Introduces CARB-Compliant MX-13 Engine

Orders Open for T680, T880, W990 Trucks; Production to Start in Q4
Kenworth T680
Paccar’s MX-13 diesel engine is now available for its T680 (shown), T880 and W990 Class 8 trucks. (TruckPR/flickr)

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Kenworth Truck Co. announced a California-compliant version of Paccar’s MX-13 diesel engine is now available for its T680, T880 and W990 Class 8 trucks.

The engine is compliant with forthcoming California Air Resources Board regulations that aim for a 90% reduction in nitrogen engine emissions compared with current diesel engines. The rules apply to model year 2024 and later medium- and heavy-duty diesel engines.

Kirkland, Wash.-based Kenworth — a Paccar brand — said orders for trucks with the CARB-compliant engine are now open and production is scheduled to begin in the fourth quarter of 2024.

“Our customers are looking for better options to successfully navigate the complexities of the evolving regulatory landscape and Kenworth models equipped with Paccar’s MX-13 CARB-compliant engine achieve compliance with stringent emissions regulations while also delivering a solution that drives increased engine efficiency and enhanced fuel economy,” said Kevin Haygood, Kenworth assistant general manager for sales and marketing.

Kevin Haygood


Kenworth’s CARB-compliant MX-13 engines are available in two options: a 510-horsepower rating with 1,850 pound-feet of torque and a 455-horsepower rating with 1,650 pound-feet of torque.

Changes to bring the engine into compliance in the Golden State included redesigned pistons, crankshaft and fuel injectors. An all-new exhaust aftertreatment system also was added.

Kenworth sister company Peterbilt Motors Co. announced June 4 that the California-compliant version of the MX-13 diesel engine was now available for its Model 579, Model 567 and Model 589 trucks.

The introduction of the engine follows the July 2023 unveiling of the Clean Truck Partnership, under which CARB and members of the Truck and Engine Manufacturers Association — including Paccar — jointly agreed to timelines for the introduction of equipment that meets the California rules.

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The group also includes fellow Class 8 truck manufacturers Daimler Truck North America, Hino, Navistar and Volvo Group North America, parent company of Volvo Trucks North America and Mack Trucks, plus engine supplier Cummins.

Under the pact, CARB agreed to relax existing state NOx pollution standards to federal levels and in return the truck makers and Cummins promised to meet the state’s zero-emission vehicle and air pollution targets.

While the engine option is primarily intended to meet California rules, other states are also adopting California’s heavy-duty regulations over the next three years. Massachusetts and Oregon, for example, are set to adopt the rules in 2025. New York, Vermont and Washington will follow suit in 2026 and a further four states are set to adopt the regulations in 2027.