PACCAR MX-13 Engine for Sale | OEM Used 12.9L Inline-6 Class 8 Truck Diesel | Direct Fit Kenworth T680, Peterbilt 579 and Related Chassis

Description

About the PACCAR MX-13 Engine

The PACCAR MX-13 engine is a testament to robust engineering and exceptional performance in the commercial trucking industry. The durable and fuel-efficient nature of this PACCAR MX-13 engine for sale at Part Nests makes it a preferred choice for Kenworth and Peterbilt truck operators who want proven PACCAR power for their Class 8 long-haul and vocational applications.

The PACCAR MX-13 Heritage

The PACCAR MX-13 is a 12.9-liter Inline-6 diesel engine, the flagship engine product from PACCAR Inc., parent company of Kenworth Truck Company, Peterbilt Motors, and European truck manufacturer DAF Trucks. The MX-13 has its roots in the DAF MX-13 engine introduced in European DAF trucks in 2005, after PACCAR acquisition of DAF in 1996 enabled global engine platform sharing.

The MX-13 was launched in North American Kenworth and Peterbilt trucks in 2010 (2011 model year), produced at PACCAR brand-new engine manufacturing facility in Columbus, Mississippi, which opened in 2010 specifically to produce the MX-13 for the North American market.

The MX-13 has gone through multiple generations to address tightening emissions and efficiency requirements:

• 2011 to 2017 MX-13: Original North American production (EPA10 / GHG14 emissions)
• 2017+ MX-13: GHG17 emissions with engine downspeeding optimizations for improved fuel economy at highway cruise
• Current MX-13: GHG21+ emissions with continuing efficiency improvements
• DAF MX-13: European market equivalent, slightly different calibrations and accessories

The MX-13 also has a smaller sibling, the PACCAR MX-11 (10.8 liter Inline-6), for lighter-duty Class 8 and Class 7 applications.

The Class 8 13L Inline-6 Competitor Family Context

For buyers comparing 12.8L to 13L Inline-6 Class 8 diesels across manufacturers, the PACCAR MX-13 competes with several other Class 8 engines in the same displacement class but from different OEMs, each tied to specific chassis brands. The PACCAR MX-13 is exclusive to PACCAR-brand chassis (Kenworth, Peterbilt, DAF in Europe). The direct competitors in the 12.8L to 13L Inline-6 Class 8 segment are: the Detroit DD13 (our vaz96 listing, 12.8L Inline-6 from Daimler, exclusive to Freightliner Cascadia and Western Star chassis); the Volvo D13 (our vaz120 listing, 12.8L Inline-6 from Volvo Trucks, exclusive to Volvo VNL / VNR / VNX / VHD chassis); and the Mack MP8 (our vaz102 listing, 13L Inline-6 sharing the same engine family as the Volvo D13 since Volvo acquired Mack in 2000-2001, exclusive to Mack Anthem / Pinnacle / Granite chassis). The four engines are NOT interchangeable across chassis brands: each is engineered with brand-specific bellhousing patterns, ECM architectures, and aftertreatment integration. Kenworth and Peterbilt buyers can alternatively spec the Cummins X15 (our vaz104 listing) as the Cummins competitor to the MX-13 within PACCAR chassis.

Condition of PACCAR MX-13 Engines

Our inventory includes used PACCAR MX-13 engines that are meticulously inspected and fully tested. The engines are categorized based on their condition:

• Used Engines: These engines are thoroughly checked for wear, with all 6 cylinders compression tested, high-pressure common rail injectors inspected, VGT turbocharger condition assessed, and emissions aftertreatment hardware (DPF / SCR / DEF / EGR cooler) condition documented before shipping.

Key Features of PACCAR MX-13 Engine

The PACCAR MX-13 engine is renowned for its advanced features:

• High-Pressure Common Rail Injection: The MX-13 uses high-pressure common rail direct injection with injection pressures up to approximately 2,500 bar (about 36,250 psi), delivering precisely-metered fuel for optimal combustion, better fuel efficiency, and reduced engine noise compared to mechanical injection systems.
• Variable Geometry Turbocharger (VGT): The MX-13 VGT optimizes turbocharger performance across the engine full operating range by varying the angle of the turbine inlet vanes, controlling boost pressure and exhaust energy recovery for both low-rpm response and high-rpm power.
• Compacted Graphite Iron (CGI) Block: The MX-13 cylinder block is cast from Compacted Graphite Iron (CGI), a material that is approximately 75% stronger and 40% stiffer than conventional gray cast iron while being lighter. CGI allows the MX-13 to handle higher peak cylinder pressures (essential for high-efficiency combustion) without weight penalty.
• Exhaust Gas Recirculation (EGR): Cooled EGR reduces NOx formation by recirculating a metered portion of exhaust gas back into the engine intake, complementing the SCR aftertreatment system for full emissions compliance.
• Integrated PACCAR Engine Brake: The MX-13 features an integrated compression-release engine brake (similar in operation to a Jacobs Engine Brake), providing significant downhill retarding power to reduce wear on the service brakes and enable safer mountain descents with heavy Class 8 loads.
• DOHC 4-Valve Cylinder Heads: Double overhead camshaft (DOHC) cylinder heads with 4 valves per cylinder (2 intake, 2 exhaust per cylinder, 24 valves total) optimize airflow into and out of the combustion chambers, enabling better volumetric efficiency, lower pumping losses, and improved fuel economy at cruise.
• Advanced Cooling System: A high-efficiency radiator and coolant system maintains optimal operating temperatures even under maximum load on mountain grades or in high-ambient-temperature conditions.
• Oil Management System: Enhanced oil filtration and cooling extends oil service intervals (typically 50,000 to 75,000 miles in linehaul service with PACCAR oil sampling program) and contributes to overall engine longevity.
• Electronic Control Module (ECM): The MX-13 ECM monitors and manages engine parameters in real-time, providing precise control of fuel injection, turbocharger boost, EGR flow, and aftertreatment dosing, with full integration into the Kenworth or Peterbilt vehicle control network for diagnostics and driver information.
• B10 Design Life of 1,000,000 Miles: PACCAR engineers the MX-13 with a B10 design life of 1,000,000 miles, meaning only 10% of engines reach end-of-life by one million miles of service, making the MX-13 one of the most durable Class 8 truck engines on the market.

The PACCAR MX-13 Engine Fits

Kenworth Trucks:

• Kenworth T680 (the dominant MX-13 application, Kenworth flagship aerodynamic long-haul truck; the T680 with MX-13 is one of the most-sold combinations in the Class 8 market)
• Kenworth T880 (Kenworth vocational and heavy-haul chassis with MX-13 power option)
• Kenworth W990 (Kenworth premium conventional long-hood truck with MX-13 option)
• Kenworth T370 (medium-heavy Class 7 / 8 vocational chassis)
• Kenworth T660 (legacy aerodynamic chassis preceding the T680, MX-13 available in later production)

Peterbilt Trucks:

• Peterbilt 579 (the dominant Peterbilt MX-13 application, Peterbilt flagship aerodynamic long-haul truck; the 579 with MX-13 mirrors the Kenworth T680 in Peterbilt branding)
• Peterbilt 567 (Peterbilt vocational and severe-duty chassis)
• Peterbilt 389 (Peterbilt premium long-hood conventional, the iconic owner-operator truck, MX-13 option)
• Peterbilt 520 (refuse and severe-duty cab-over chassis)
• Peterbilt 365 (vocational and heavy-haul chassis)

DAF Trucks (European market, sold as DAF MX-13):

• DAF XF (the European flagship long-haul truck)
• DAF CF (DAF distribution and regional-haul chassis)
• DAF LF (DAF lighter-duty chassis; lighter MX-11 also available)

Common Transmission Pairings With MX-13

The MX-13 is commonly paired with:

• Eaton Fuller manual transmissions (10-speed, 13-speed, and 18-speed Fuller Roadranger; the 18-speed Roadranger is our vaz130 listing, dominant in line-haul applications)
• Eaton Fuller UltraShift PLUS automated manual transmission
• PACCAR TX-12 automated manual transmission (PACCAR own AMT, increasingly popular in current production)
• Allison automatic transmissions (vocational chassis applications)

Condition

Our used PACCAR MX-13 engines are well-maintained and in working condition. Each engine has been previously used in Class 8 commercial trucking service, with full documentation of donor truck application, mileage, and service history where available.

Signs You Need a Replacement PACCAR MX-13

• Loss of compression on one or more cylinders
• High-pressure common rail injector failure (a documented MX-13 service item at high mileage)
• VGT turbocharger failure (vane sticking, bearing wear, boost loss)
• EGR cooler failure (coolant in oil, coolant in EGR pipe, white exhaust smoke)
• DPF aftertreatment failure (excessive regeneration cycles, derate conditions)
• SCR / DEF system failure (DEF doser issues, NOx sensor failure)
• Connecting rod or main bearing knock under load
• Cylinder head crack symptoms (coolant in oil, white smoke, overheating)
• Donor Kenworth or Peterbilt totaled or retired and the MX-13 is being moved to another chassis
• Fleet repower project requiring proven PACCAR MX-13 reliability for owner-operator or small-fleet operations

Common MX-13 Maintenance Considerations

• Oil service: Use PACCAR Specification 1100098 Genuine PACCAR Oil (or compatible API CK-4 spec heavy-duty diesel engine oil). Service intervals 50,000 to 75,000 miles with PACCAR oil sampling program.
• Fuel filters: CRITICAL for high-pressure common rail injector longevity. Change fuel filters at every oil service. Contaminated fuel is the leading cause of common rail injector failure.
• DEF service: Diesel Exhaust Fluid is consumed at approximately 2-3% of diesel fuel rate. Monitor DEF level and quality. Use only API-certified DEF.
• DPF regeneration: Active and passive DPF regeneration occurs automatically. Avoid extended low-load operation (idling, short trips) that prevents passive regen.
• Coolant service: Use PACCAR-approved heavy-duty extended life coolant. Service every 600,000 miles or 6 years with proper SCA (Supplemental Coolant Additive) maintenance.
• Valve adjustment: Periodic valve clearance check per PACCAR service interval (typically at major service points).
• Engine brake service: Periodic inspection of PACCAR engine brake solenoids and oil supply.

What Ships and What Does Not

Vehicle Compatibility

The PACCAR MX-13 fits the following major Class 8 truck applications:

Tell us your specific truck and we will confirm matching MX-13 generation, ECM compatibility, and emissions aftertreatment configuration.

Inspection Workflow

Every used PACCAR MX-13 we ship goes through this process:

• All 6 cylinders compression tested, pressure per cylinder recorded
• Generation authenticated (EPA10 / GHG14, GHG17, or GHG21+)
• High-pressure common rail fuel system inspected (injectors, rail, high-pressure pump)
• VGT turbocharger condition assessed (vane movement, shaft play, bearing wear)
• EGR cooler condition documented
• DPF / SCR / DEF aftertreatment hardware condition documented (when included with the engine)
• PACCAR engine brake operation verified
• Top-end inspection (DOHC heads, camshafts, valve train)
• CGI block visual inspection for cracks
• Donor truck photographed and documented
• Mileage documented when verifiable from ECM data or service records

Why Buy From Part Nests

• All 6 cylinders compression tested, results before you pay
• Generation authenticated (EPA10 / GHG14, GHG17, or GHG21+ confirmed)
• High-pressure common rail fuel system inspected
• VGT turbocharger condition assessed (vane movement specifically tested)
• EGR cooler condition documented (a known MX-13 service point)
• PACCAR engine brake operation verified
• Top-end DOHC inspection (camshafts, valve train, 4-valve heads)
• CGI block visual inspection (the MX-13 defining strength feature)
• Donor truck traced (Kenworth T680, T880, W990, T370, T660 or Peterbilt 579, 567, 389, 520, 365)
• Mileage documented when verifiable
• Free crated freight delivery to all 48 contiguous states
• 15 day replacement warranty on internal defects
• PACCAR-experienced support team on the phone with knowledge of MX-13 generation differences
• Call (855) 634-4447 to confirm PACCAR MX-13 chassis compatibility (Kenworth T680 / T880 / W990 / T370 / T660 or Peterbilt 579 / 567 / 389 / 520 / 365 only, NOT the Detroit DD13 per vaz96 for Freightliner / Western Star, NOT the Volvo D13 per vaz120 for Volvo, NOT the Mack MP8 per vaz102 for Mack), generation (EPA10 / GHG14, GHG17 downspeeding, or GHG21+), Cummins X15 per vaz104 as the alternative Cummins option in Kenworth / Peterbilt, transmission pairing (Eaton Fuller 18-speed Roadranger per vaz130, UltraShift PLUS, PACCAR TX-12 AMT, or Allison automatic), and the PACCAR Specification 1100098 oil requirement before ordering