Cummins X12
11.80L Inline-6 turbo diesel • Cummins
About the Cummins X12
The Cummins X12 is Cummins' 11.8L mid-displacement Class 8 engine — bridging the gap between the L9 (8.9L medium-heavy) and the X15 (15L heavy-duty). Launched 2019 for regional haul and vocational applications where the X15 is overkill but the L9 is undersized. The X12 is lighter (~600 lb less than X15), which improves payload by an equivalent amount — meaningful for weight-sensitive carriers. Used in Freightliner Cascadia, Kenworth T680, Peterbilt 579, Volvo VNR, and Mack Anthem in regional configurations.
Overview
The Cummins X12 is Cummins' 11.8L mid-displacement Class 8 engine — bridging the gap between the L9 (8.9L medium-heavy) and the X15 (15L heavy-duty). Launched 2019 for regional haul and vocational applications where the X15 is overkill but the L9 is undersized. The X12 is lighter (~600 lb less than X15), which improves payload by an equivalent amount — meaningful for weight-sensitive carriers. Used in Freightliner Cascadia, Kenworth T680, Peterbilt 579, Volvo VNR, and Mack Anthem in regional configurations.
Specifications
- Manufacturer
- Cummins
- Displacement
- 11.80 liters
- Configuration
- Inline-6 turbo diesel
- Fuel type
- Diesel
- Horsepower
- 350–500 hp
- Torque
- 1250–1700 lb-ft
- Production years
- 2019–present
- Truck classes
- Class 8
- Applications
- Regional haul, vocational, medium-heavy Class 8
Design and engineering
11.8L inline-6, parent-bore block (not wet-sleeve like the X15), variable geometry turbocharger, SCR + DEF aftertreatment. Lighter than X15 by ~600 lb. Common rail injection.
Generations and emissions eras
Reliability and longevity
Cummins-grade reliability, but parent-bore block (not wet-sleeve like X15) means rebuilds at high mileage require block replacement vs in-frame liner replacement. Better suited to lighter-duty applications.
Common problems
DEF/SCR issues at 300K+ miles (industry-wide). NOx sensor degradation. EGR cooler can crack with severe-duty use.
Pros and cons
✓ Pros
- • 600 lb lighter than X15 → more payload
- • Right-sized for regional/vocational
- • Cummins service network
- • Better fuel economy than X15 in light loads
⚠ Cons
- • Parent-bore block — rebuild costlier than X15
- • Lower power max than X15
- • Not ideal for heavy-haul