PACCAR MX-13
12.90L Inline-6 turbo diesel • PACCAR
About the PACCAR MX-13
The PACCAR MX-13 is PACCAR's in-house 12.9L inline-6 turbo diesel, used in Peterbilt and Kenworth trucks. PACCAR introduced the MX-13 in 2010 to reduce dependence on Cummins (PACCAR's primary engine supplier for decades). The MX-13 is based on the European PACCAR DAF XE platform but engineered specifically for North American duty cycles. Modern MX-13 (2020+) has improved significantly over earlier versions — initial 2010-2015 MX-13 engines had reliability issues that hurt PACCAR brand reputation, but the 2020+ updates have largely closed the gap with Cummins X15 and Detroit DD15.
Overview
The PACCAR MX-13 is PACCAR's in-house 12.9L inline-6 turbo diesel, used in Peterbilt and Kenworth trucks. PACCAR introduced the MX-13 in 2010 to reduce dependence on Cummins (PACCAR's primary engine supplier for decades). The MX-13 is based on the European PACCAR DAF XE platform but engineered specifically for North American duty cycles. Modern MX-13 (2020+) has improved significantly over earlier versions — initial 2010-2015 MX-13 engines had reliability issues that hurt PACCAR brand reputation, but the 2020+ updates have largely closed the gap with Cummins X15 and Detroit DD15.
Specifications
- Manufacturer
- PACCAR
- Displacement
- 12.90 liters
- Configuration
- Inline-6 turbo diesel
- Fuel type
- Diesel
- Horsepower
- 380–510 hp
- Torque
- 1450–1850 lb-ft
- Production years
- 2010–present
- Truck classes
- Class 8
- Applications
- Long haul, regional, vocational
Design and engineering
12.9L inline-6 with cast iron block (parent bore, not wet sleeve). Variable geometry turbocharger. Common rail fuel system. EPA 2017-compliant SCR aftertreatment. The MX-13 is shorter and lighter than the X15 or DD15 (15L engines), giving Peterbilt and Kenworth trucks payload advantages.
Generations and emissions eras
Reliability and longevity
2020+ MX-13 is reliable — comparable to Cummins X15 and Detroit DD15 in independent fleet surveys. 2010-2015 MX-13 was problematic — many trucks needed second engines before 500K miles. 2016-2019 MX-13 improved but still trailed Cummins. PACCAR brand reputation is still recovering from the early MX-13 era.
Common problems
All eras: EGR cooler failures (the most consistent issue — 2010-2015 most severe, improved 2016+). Turbocharger wear at 400K-600K miles. DEF system issues at 200K+ miles. 2010-2015 head gasket failures (largely resolved 2016+). Cam follower wear on certain production years.
Maintenance schedule
Engine oil every 40,000-50,000 miles. Fuel filters every 20,000 miles. Coolant flush every 500,000 miles. DPF cleaning every 400,000 miles. EGR cooler inspection recommended at 300,000 miles.
Pros and cons
✓ Pros
- • Lighter than 15L engines (payload advantage)
- • Modern 2020+ MX-13 is reliable
- • Strong PACCAR financing programs
- • Integrated with PACCAR TX-12 transmission
- • Lower acquisition cost than Cummins X15 spec
⚠ Cons
- • Earlier generations (2010-2015) had serious reliability issues
- • Parent-bore block — expensive at full rebuild
- • Smaller used market than Cummins X15
- • Lower resale than X15-equipped trucks
Resale value impact
MX-13-equipped Peterbilt/Kenworth trucks have lower resale than equivalent Cummins X15 trucks — typically $5,000-12,000 less at 3-5 years old. The gap is larger for owner-operator-oriented trucks (Peterbilt 389, Kenworth W900) and smaller for fleet-spec trucks (Peterbilt 579, Kenworth T680).