Caterpillar C15 Cat Engine for Sale | OEM Used 15.2L Inline-6 Turbocharged Diesel for Class 8 Trucks
$46,500.00
At a Glance
- Condition: OEM used, top-end inspected and ECM-documented before shipping
- Availability: In stock, pre-ACERT 6NZ and ACERT (MXS / SDP / 6TZ) variants available
- Shipping: Free shipping to all 50 states via crated freight, 7 to 14 business days
- Variant confirmed (pre-ACERT 6NZ vs ACERT MXS / SDP / 6TZ)
- ECM serial number documented for Cat Connect compatibility
- Turbocharger and air-to-air aftercooler inspected
- Top-end condition inspected (heads, injectors, rocker arms)
- MEUI injector operation verified where possible
- Donor truck documented (Freightliner, Kenworth, Peterbilt, Mack, International, Western Star)
- 100% inspection before every order ships
- Backed by a 15 day replacement warranty against internal defects
Description
About the Caterpillar C15 Cat Engine
Renowned for its durability and performance, the Caterpillar C15 engine is highly sought after across multiple industries. The C15 Engine for sale at Part Nests is a powerful Class 8 truck diesel with proven reliability. Though used, this motor is the perfect solution for your over-the-road trucking, vocational, and commercial needs.
The Caterpillar C15 engine is a powerhouse, delivering exceptional performance in heavy-duty applications. From Class 8 trucks to industrial machinery, the C15 engine for sale is designed to meet the rigorous demands of various operational environments.
The C15 Family Tree, Pre-ACERT vs ACERT
The C15 was offered in two main generations across its production life:
| Option | Description |
|---|---|
| Pre-ACERT C15 (6NZ Series, 1999 to 2003) | The original C15, replacing the 3406E in 1999. Beloved by owner-operators for its raw simplicity, mechanical-feel character, and exceptional tunability. The 6NZ designation refers to the engine serial number prefix. The pre-ACERT C15 has no EGR (Exhaust Gas Recirculation), making it a favorite among performance-tuning shops because it can support 800+ hp with appropriate tuning and supporting modifications. |
| ACERT C15 (MXS, SDP, 6TZ Series, 2004 to 2007) | The C15 with ACERT technology (Advanced Combustion Emission Reduction Technologies), Caterpillar’s solution to meeting EPA 2004-2007 emissions regulations. ACERT introduced Variable Valve Actuation (VVA) and Exhaust Gas Recirculation (EGR). The MXS, SDP, and 6TZ engine serial number prefixes designate sub-variants with progressively updated emissions controls. ACERT engines are more emissions-compliant but more complex to service. |
After 2007, Caterpillar exited the on-highway truck engine market in North America, making the late ACERT C15 variants the last “Cat Truck Engine” available new (until the modern CT-15 / Cat Industrial C15 platform). This historical position adds collector and restoration value to documented C15 cores.
The C15 Cat Family Lineage
The C15 replaced the legendary 3406E in 1999, continuing the Caterpillar Class 8 engine line. The full lineage that buyers should understand:
- 3406B (1980-1987, our vaz83 listing): Mechanical fuel injection, ATAAC aftercooled. Pre-electronic generation.
- 3406C (1988-1993): Mechanical sleeve metering fuel system, transitional generation.
- 3406E (1993-1998, our vaz61 listing): First electronic 3406, HEUI fuel injection, ECM-controlled.
- C15 (1999-2007, THIS LISTING): Pre-ACERT 6NZ (1999-2003) and ACERT MXS / SDP / 6TZ (2004-2007). MEUI fuel system, modern ECM.
Features of the C15 Engine
- MEUI Fuel System: Fuel injection is performed by MEUI (Mechanically Actuated, Electronically Controlled Unit Injection), which combines mechanical actuation with electronic control of injection timing and quantity. This delivers precise fuel control for performance and economy.
- Turbocharging and Aftercooling: The C15 features a turbocharger and air-to-air aftercooler for high-efficiency air intake, which improves power delivery and fuel consumption while keeping intake air temperatures controlled.
- Robust Design: Built with a cast iron block, forged steel crankshaft, and high-quality components designed to withstand the abuse of Class 8 trucking duty cycles.
- Overhead Valve (OHV) Configuration: OHV with 4 valves per cylinder (2 intake, 2 exhaust) provides good breathing while maintaining the simpler service architecture of OHV vs OHC engines.
- ACERT Technology: ACERT (Advanced Combustion Emission Reduction Technologies) on 2004-2007 variants reduces particulate matter and NOx emissions through optimized combustion timing, VVA, and EGR.
- Exhaust Gas Recirculation (EGR): On ACERT variants, EGR reduces nitrogen oxide (NOx) emissions to meet 2004-2007 EPA standards.
- Electronic Control Module (ECM): Caterpillar ECM regulates fuel injection, air management, EGR (on ACERT), and VVA (on ACERT). The ECM also provides Cat ET diagnostic capability and stores fault history.
- High Torque at Low RPM: The C15 produces peak torque of 2,050 lb-ft at low rpm, providing excellent low-end pulling power for hauling heavy gross combination weight (GCW) loads.
- Variable Valve Actuation (VVA): ACERT variants use VVA to optimize valve timing for emissions and efficiency across the rpm range.
- Engineered Cooling System: The C15 cooling system is sized for sustained heavy-duty operation, keeping engine temperatures stable under maximum-load operation.
Models and Variants
We offer several models of the C15 Cat engine for sale, including pre-ACERT 6NZ and ACERT (MXS, SDP, 6TZ) variants. These engines are available in various configurations to ensure they meet your particular requirements. Tell us your truck year, donor truck (Freightliner Classic XL, Kenworth T800, Peterbilt 389, etc.), and ECM compatibility requirements, and we will match the appropriate variant.
Common C15 Applications
- Class 8 Heavy-Duty Trucks: Freightliner Classic XL, Freightliner Coronado, Kenworth T800, Kenworth W900, Peterbilt 379, Peterbilt 389, Peterbilt 365, Mack (Caterpillar engine option), International, Western Star 4900, Western Star 5900
- Marine Propulsion: Commercial vessels using C15 marine variants for tug and workboat applications
- Industrial / Power Generation: C15-based generator sets and stationary power applications
- Mining and Construction: Heavy haul mining trucks and construction equipment
Signs You Need a Replacement C15
- Loss of compression on one or more cylinders (low oil pressure on cold start, blue smoke, oil consumption)
- MEUI injector failure (rough running, high EGR fault codes, smoke)
- Turbocharger failure (boost drop, blue oil smoke, whistle / surge sounds)
- Cylinder head crack (coolant in oil, white smoke, overheating)
- Connecting rod or main bearing knock under load
- ACERT-specific: VVA solenoid wear, EGR cooler failure (on MXS / SDP / 6TZ variants)
- Donor truck has been totaled and the C15 is being moved to a different chassis
- High-mileage repower of an aging Class 8 truck
Condition and Quality Assurance
Our inventory includes high-quality, thoroughly inspected used C15 engines for sale. Each engine undergoes rigorous testing to ensure it meets our stringent standards for performance and reliability. We pride ourselves on providing engines that are not only affordable but also dependable.
Here at Part Nests, you will find the best quality used C15 engine for sale at a very reasonable price.
What Ships and What Does Not
| Item | Details |
|---|---|
| INCLUDED | Long block: cast iron block, forged crankshaft, connecting rods, pistons, camshaft, cylinder heads, valve train, MEUI injectors (typical), turbocharger (typical), oil pan, valve covers. |
| NOT INCLUDED | ECM (sold separately, application-specific to truck chassis and ECM serial number requirements), wiring harness, intake manifold (typical), exhaust manifold (typical), starter, alternator, A/C compressor, water pump, thermostat, oil cooler, transmission, motor mounts. |
| Fluids | Drained before shipping. Refill with Cat-approved engine oil meeting ECF-3 spec or higher (15W-40 mineral or synthetic per Cat operating manual). |
| Provenance Note | Donor truck application disclosed where available. ECM serial number documented for buyer’s Cat ET / Cat Connect compatibility verification. |
| Core Note | No core charge. You are not required to return your old engine. |
Vehicle Compatibility
The Caterpillar C15 was used in the following Class 8 truck applications:
| Vehicle | Compatibility |
|---|---|
| Freightliner Classic XL | The classic owner-operator C15 application |
| Freightliner Coronado | Cat C15 was a popular engine option |
| Freightliner Columbia | Cat C15 option (with the 3406E predecessor in earlier years) |
| Kenworth T800 | Cat C15 was the premium engine option |
| Kenworth W900 | Cat C15 was the premium engine option for the iconic long-hood |
| Peterbilt 379 | Cat C15 was the premium owner-operator engine option |
| Peterbilt 389 | Cat C15 was the premium engine option for the modern long-hood |
| Peterbilt 365 | Cat C15 vocational option |
| Mack Trucks | Caterpillar engine option in Mack chassis |
| International Trucks | Cat C15 engine option in International heavy-duty trucks |
| Western Star 4900 | Cat C15 was a popular engine option |
| Western Star 5900 | Cat C15 was a popular engine option |
Industrial / marine / mining variants exist with different ECM calibrations. Tell us your application and we will match the appropriate C15.
Inspection Workflow
Every used Caterpillar C15 we ship goes through this process:
- Variant confirmed (pre-ACERT 6NZ vs ACERT MXS / SDP / 6TZ)
- ECM serial number documented for Cat Connect / Cat ET compatibility
- Cylinder head visual inspection for cracks
- Top-end inspection (heads, injector cups, rocker arms)
- MEUI injector operation tested where possible
- Turbocharger inspected for shaft play and bearing wear
- Air-to-air aftercooler condition inspected
- Donor truck application photographed and documented
- Approximate hours / mileage documented when verifiable from donor
Why Buy From Part Nests
- Variant authenticated (pre-ACERT 6NZ vs ACERT MXS / SDP / 6TZ) for ECM compatibility
- ECM serial number documented for Cat ET / Cat Connect verification
- Top-end inspection (heads, injectors, rocker arms)
- MEUI injector operation tested where possible
- Turbocharger and air-to-air aftercooler inspected
- Donor truck traced (Freightliner Classic XL, Kenworth T800, Peterbilt 389, etc.)
- Crated freight delivery to all 50 states for vintage / Class 8 engines
- 15 day replacement warranty on internal defects
- Cat-experienced support team on the phone with knowledge of pre-ACERT vs ACERT differences
- Call (240) 306-7051 to confirm variant (pre-ACERT 6NZ vs ACERT MXS / SDP / 6TZ), ECM serial number for Cat Connect, donor truck application, and predecessor / successor lineage questions (3406B per vaz83, 3406E per vaz61, C15 per this listing) before ordering
15 Day Replacement Warranty
Every used Caterpillar C15 engine purchased through Part Nests carries a 15 day replacement warranty starting on the delivery date.
What Is Covered
- Internal defects already present when the engine arrives
- Compression failures on any of the 6 cylinders beyond what was disclosed
- Cylinder head crack failures within 15 days from installation (where head was documented as crack-free at shipping)
- MEUI injector failures within 15 days from installation (where injector operation was documented at shipping)
- Turbocharger failures within 15 days from installation (where turbo was documented as functional at shipping)
- VVA solenoid failures within 15 days from installation on ACERT variants
- Connecting rod, lifter, or bearing failures within 15 days from installation
- Incorrect variant shipped (pre-ACERT 6NZ vs ACERT MXS / SDP / 6TZ) due to an error on our end
What Is Not Covered
- Damage caused during installation
- Damage from running with contaminated fuel (water, dirt, particulates)
- Damage from extended oil change intervals or incorrect oil viscosity (Cat-approved ECF-3 or higher 15W-40 required)
- Damage from operating with incorrect coolant or neglected cooling system
- Damage from aggressive aftermarket tuning beyond Cat-approved fuel maps (the pre-ACERT 6NZ can support 800-plus hp tuned, but with potential durability tradeoffs)
- EGR-related failures on ACERT variants if the EGR cooler has been deleted or modified
- External components (ECM if separately documented, turbocharger if separately documented, harness, intake manifold, exhaust manifold, starter, alternator, A/C, water pump, oil cooler) unless itemized
- Labor expenses of any kind
To start a warranty claim, reach us within 15 days of delivery at (855) 634-4447.
- Variant Confirmed: Pre-ACERT 6NZ or ACERT MXS / SDP / 6TZ documented for ECM matching
- ECM Serial Number Documented: Cat Connect / Cat ET compatibility verifiable
- Top-End Inspection: Heads, MEUI injector cups, rocker arms assessed
- Turbocharger Inspected: Shaft play and bearing wear evaluated
- Cat Family Lineage Preserved: Successor to 3406E (vaz61) and 3406B (vaz83)
- 15 Day Replacement Cover: Internal defects protected from delivery onward
Additional information
| aspiration | Turbocharged with air-to-air aftercooler |
|---|---|
| bore-x-stroke | 5.4 in x 6.75 in |
| compression-ratio | 16.0:1 |
| configuration | Inline-6 |
| cooling-system | Liquid-cooled |
| fuel-system | MEUI (Mechanically Actuated, Electronically Controlled Unit Injection) |
| intake | Turbocharged with intercooler / aftercooler |
Two generations distinguished by emissions controls. The pre-ACERT C15 (6NZ Series, 1999-2003) replaced the 3406E in 1999 and is beloved by owner-operators for its raw simplicity and tunability. The 6NZ designation refers to the engine serial number prefix. The pre-ACERT C15 has no EGR (Exhaust Gas Recirculation), no VVA (Variable Valve Actuation), and can support 800-plus hp with appropriate tuning and supporting modifications. The ACERT C15 (MXS, SDP, 6TZ Series, 2004-2007) added ACERT technology to meet EPA 2004-2007 emissions: VVA, EGR cooler, refined combustion timing. ACERT engines are more emissions-compliant but more complex to service. The MXS, SDP, and 6TZ ECM serial prefixes designate sub-variants with progressively updated emissions controls.
The C15 replaced the 3406E in 1999, continuing the Cat Class 8 engine lineage. The full family: 3406B (1980-1987, our vaz83 listing, mechanical fuel injection, ATAAC aftercooled), 3406C (1988-1993, mechanical sleeve metering, transitional), 3406E (1993-1998, our vaz61 listing, first electronic 3406 with HEUI fuel injection), C15 (1999-2007 with pre-ACERT 6NZ then ACERT MXS / SDP / 6TZ, MEUI fuel system). After 2007, Caterpillar exited the on-highway truck engine market in North America. Modern Cat continuation is through the industrial C15 / CT-15 platforms for marine, industrial, and mining applications. This makes the 2007 ACERT C15 the last on-highway Cat truck engine available new.
Mechanically Actuated, Electronically Controlled Unit Injection. MEUI is Caterpillar fuel injection system that combines mechanical actuation (via the engine camshaft) with electronic control of injection timing and quantity (via the ECM). Each cylinder has its own MEUI unit injector mounted in the cylinder head. The camshaft physically actuates the injector plunger, while the ECM controls the timing and duration of the injection event via solenoid valves on the injector. This delivers precise fuel control for performance and emissions while retaining the mechanical reliability of cam-actuated injection. MEUI is different from HEUI (used on the 3406E and Ford 7.3 Powerstroke), which uses high-pressure engine oil to actuate the injectors.
No EGR, simpler emissions architecture, tunability headroom up to 800-plus hp. The pre-ACERT C15 (6NZ, 1999-2003) was manufactured before the EPA 2004-2007 emissions standards required EGR, VVA, and other complex emissions controls. This means no EGR cooler to fail, no VVA solenoids to wear, and a simpler architecture to service. Owner-operators particularly value the 6NZ because performance tuning shops can extract substantial additional power from the C15 platform; well-built 6NZ engines have been documented producing 800-plus hp on stock bottom ends with appropriate fuel system, turbo, and air-handling upgrades. The 6NZ is the Cat equivalent of the Cummins N14 Celect Plus (our vaz74 listing) in pre-emissions desirability.
Class 8 conventional cab tractors. Most commonly: Freightliner Classic XL (the classic owner-operator C15 application), Freightliner Coronado, Freightliner Columbia (Cat option, with the 3406E predecessor in earlier years), Kenworth T800 (Cat C15 premium engine option), Kenworth W900 (Cat C15 premium engine for the iconic long-hood), Peterbilt 379 (Cat C15 premium owner-operator option), Peterbilt 389 (Cat C15 modern long-hood), Peterbilt 365 (Cat C15 vocational), Mack Trucks (Cat engine option), International, Western Star 4900, Western Star 5900. Also found in industrial generators, marine vessels, and mining applications with different ECM calibrations.
Multiple ratings depending on year and ECM calibration. The C15 was offered across its 1999-2007 production with horsepower ratings from approximately 435 hp through 625 hp at peak torque of 2,050 lb-ft. Common owner-operator ratings: 475, 500, 550, 600, 625 hp. The pre-ACERT 6NZ specifically is known for tuning headroom; performance shops have built 6NZ engines to 800-plus hp with supporting hardware. ACERT variants have slightly different rating ranges due to the emissions calibration. We document the original factory rating where verifiable from the donor truck.
Cat ET / Cat Connect compatibility verification. Cat engines use the ECM serial number as a critical identifier for diagnostic software compatibility, parts lookups, and warranty/service history queries. The ECM serial number is documented on every C15 we ship so the buyer can verify Cat ET (Cat Electronic Technician) diagnostic software compatibility, Cat Connect telematics integration if equipped, and proper service procedure references. For installation in a different chassis, the ECM may need to be flashed with the new application's parameter file via a Cat-authorized dealer. We provide the ECM serial number information to support buyer due diligence.
No. There is no core return required.
2 reviews for Caterpillar C15 Cat Engine for Sale | OEM Used 15.2L Inline-6 Turbocharged Diesel for Class 8 Trucks
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Calvin H. –
Got a pre-ACERT 6NZ C15 for a 2002 Peterbilt 379 owner-operator rebuild. Variant correctly identified as pre-ACERT 6NZ (not the later ACERT MXS / SDP / 6TZ), ECM serial number documented for Cat ET verification, top-end inspection clean, MEUI injectors tested. Honest pre-purchase information about the 6NZ tunability advantage (up to 800-plus hp documented) and the natural lineage from the 3406E predecessor (vaz61 listing).
Vivienne K. –
Sourced an ACERT C15 (MXS series) for a 2006 Freightliner Classic XL repower. ACERT generation correctly identified with VVA and EGR cooler documented, ECM serial number captured. Honest pre-purchase information about the ACERT vs pre-ACERT 6NZ differences and the EGR cooler service item on ACERT variants. Foundation for the long-haul build.