The Cummins ISX15 is a 14.9-liter inline six-cylinder heavy-duty diesel engine. It produces 400 to 600 horsepower and 1,450 to 2,050 lb-ft of torque, depending on the rating. The ISX15 uses a dual overhead camshaft design, a high-pressure common rail fuel system, and a variable geometry turbocharger. It has a cast iron block, wet replaceable cylinder liners, and a dry weight of about 2,960 pounds. First badged as the ISX15 in 2010 for EPA emissions rules, it powers Class 8 trucks like the Freightliner Cascadia, Kenworth T680, and Peterbilt 579.
That is the quick answer. The rest of this guide breaks down every Cummins ISX15 specification in detail: displacement, power ratings, fuel system, turbo, emissions equipment, fluid capacities, weight, and the ECM versions across model years. Whether you are planning a swap or verifying specs before you buy, this page has the numbers you need.
What Is the Cummins ISX15 Engine?
The Cummins ISX15 is the flagship heavy-duty engine in the Cummins ISX platform. The ISX line debuted in 1998 to replace the legendary N14, bringing electronic controls and a modern fuel system to Cummins big-bore power.
The ISX15 name became standard in 2010, when Cummins updated the engine to meet EPA 2010 emissions rules. It kept the proven 15-liter platform and added advanced emissions technology. Today it is one of the most widely used truck engines in North America, valued for its power, durability, and huge parts network.
HD Engines has supplied Cummins diesel engines for more than 25 years. You can see available units, each listed with its horsepower and emissions rating, on our Cummins ISX15 engines collection page.
Cummins ISX15 Engine Specs at a Glance
Here are the core Cummins ISX15 specifications every buyer and technician should know:
- Engine type: Inline 6-cylinder, 4-stroke diesel
- Displacement: 14.9 liters (912 cubic inches)
- Bore and stroke: 137 mm x 169 mm (5.39 in x 6.65 in)
- Horsepower range: 400 to 600 hp
- Torque range: 1,450 to 2,050 lb-ft
- Compression ratio: approximately 17:1
- Dry weight: approximately 2,960 lb (1,342 kg)
The ISX15 uses a cast iron block and cylinder head for strength, plus a dual overhead camshaft (DOHC) design with 24 valves. This layout supports the high fuel pressure and precise valve timing the engine needs for both power and efficiency.
Cummins ISX15 Fuel System and Turbocharger
The ISX15 uses a high-pressure common rail (HPCR) fuel system. This delivers fuel to each cylinder at very high pressure with precise electronic timing, which improves both power and fuel economy while lowering emissions.
Air is supplied by a variable geometry turbocharger (VGT). The turbo's adjustable vanes let the engine build boost quickly at low RPM and stay efficient at cruising speed. The VGT also works with the integrated engine brake, known as the Intebrake, to improve control on downgrades.
The fuel injectors and turbo are among the components that need periodic service over the engine's life. Keeping fuel filters fresh and clean protects the injectors, which are precision parts that operate under extreme pressure.
Need help finding the right ISX15? Share your ESN or VIN and we’ll confirm the correct engine for your truck.
Cummins ISX15 Emissions and Aftertreatment
The ISX15 was built across several emissions eras, and the aftertreatment setup changed with each one. Knowing the emissions rating matters a lot when buying used, since it must match your truck's registration.
EPA 2010 and later ISX15 engines use a full aftertreatment system: cooled exhaust gas recirculation (EGR), a diesel particulate filter (DPF), and selective catalytic reduction (SCR) with diesel exhaust fluid (DEF). Earlier EPA 2007 units used EGR and a DPF without SCR.
The emissions components, such as the EGR cooler, DEF sensors, and DPF, are the parts most likely to need attention over time. They are repairable, and staying on top of DEF quality and sensor faults prevents most emissions-related downtime.
Cummins ISX15 Oil, Coolant, and Fluid Capacities
Staying within spec on fluids is the biggest factor in how long an ISX15 lasts. Here are the key capacities to know:
- Engine oil capacity: approximately 42 quarts (10.5 gallons) with filter
- Recommended oil: 15W-40 or 10W-30 meeting Cummins CES 20081 spec
- Coolant capacity: approximately 12 to 14 gallons for the full system
- Oil change interval: up to 40,000 miles on long-haul with premium oil and monitoring
Always confirm the exact capacity against your specific engine, since intervals and volumes vary slightly by model year and application. A quick oil analysis program helps you catch wear early and extend engine life.
Cummins ISX15 ECM Versions by Model Year
The ISX15's electronic control module (ECM) changed over the years, and knowing which one an engine uses helps confirm its age and features. The main versions are:
- CM871: EPA 2007 era engines
- CM2250: EPA 2010 era engines
- CM2350: EPA 2013 and later engines
The ECM version is a reliable way to date a used ISX15 and confirm its emissions generation. When you check an engine, matching the ECM to the serial number tells you a lot about what you are buying.
Want to verify a used ISX15 before buying? Send us the engine serial number and we’ll help confirm the year and ECM.
Cummins ISX15 Horsepower and Torque Ratings
The ISX15 was offered in a wide range of factory calibrations, set by the ECM. Common ratings include:
- 400 hp with 1,450 lb-ft
- 450 hp with 1,650 lb-ft
- 500 hp with 1,850 lb-ft
- 550 hp with 1,850 to 1,950 lb-ft
- 600 hp with 2,050 lb-ft
The 450 to 500 hp ratings are the most common for long-haul trucks, balancing pulling power with fuel economy. The 600 hp rating is reserved for the heaviest loads and steepest grades. Because the rating is set in software, two physically identical engines can carry different horsepower.
Which Trucks Use the Cummins ISX15?
Unlike a brand-specific engine, the ISX15 fits a wide range of truck makes. That broad fitment is one of its biggest advantages, since parts and service are available almost everywhere.
Common ISX15 trucks include the Freightliner Cascadia, Kenworth T680 and W900, Peterbilt 579 and 389, International ProStar and LoneStar, and Western Star models. It also appears in heavy vocational trucks like dump trucks, mixers, and tankers.
If your truck runs a different engine, we stock many alternatives. The larger Cummins lineup includes the newer Cummins X15, which replaced the ISX15, and the mid-range Cummins ISX12 for lighter applications.
Is the Cummins ISX15 a Reliable Engine?
Yes. The ISX15 has a strong reputation for durability, with many engines running well past a million miles before a major overhaul. Its cast iron construction and wet replaceable liners make it a rebuild-friendly engine that can be restored to like-new condition.
As with any modern diesel, the emissions system is where most issues show up. The core engine is built tough. Regular oil changes, clean fuel, and prompt attention to emissions faults keep an ISX15 running for the long haul.
The ISX15 shares its heavy-duty class with engines like the Detroit DD15 and the Volvo D13, each with its own strengths for long-haul work.
Why ISX15 Specs Matter When Buying
Knowing the specs protects you when buying a used ISX15. The displacement and block are the same across the range, but the horsepower rating, emissions generation, and ECM version all affect fit and value.
Before buying, confirm the engine serial number, the ECM version, and the emissions rating, and make sure the horsepower rating suits your loads. Matching these details to your truck avoids compliance problems and ensures a smooth installation.
You can compare ISX15 units alongside the full Cummins range on our Cummins engines collection, or browse every brand we carry on the page.
Cummins ISX15 Specs: Frequently Asked Questions
How much horsepower does a Cummins ISX15 have?
The Cummins ISX15 produces between 400 and 600 horsepower depending on the ECM rating. The 450 to 500 hp ratings are the most common for long-haul trucks, while 600 hp is used for the heaviest loads.
What is the displacement of the Cummins ISX15?
The Cummins ISX15 has a displacement of 14.9 liters (912 cubic inches) from an inline six-cylinder design with a 137 mm bore and 169 mm stroke.
How much does a Cummins ISX15 weigh?
A Cummins ISX15 weighs approximately 2,960 pounds (1,342 kg) dry. Plan for lifting equipment rated above 3,000 pounds when handling the engine.
What oil capacity does the Cummins ISX15 have?
The Cummins ISX15 holds approximately 42 quarts (10.5 gallons) of oil with the filter, using 15W-40 or 10W-30 oil that meets the Cummins CES 20081 specification.
What is the difference between the CM2250 and CM2350 ECM?
The CM2250 ECM is used on EPA 2010 era ISX15 engines, while the CM2350 is used on EPA 2013 and later engines. The ECM version helps confirm the engine's model year and emissions generation.
How many miles does a Cummins ISX15 last?
With proper maintenance, a Cummins ISX15 commonly lasts well over 1,000,000 miles before needing a major overhaul. Its rebuild-friendly design with wet replaceable liners helps extend its service life.
Find the Right Cummins ISX15 at HD Engines
HD Engines has supplied tested Cummins engines since 1998 from our facility in Hialeah, Florida. Every ISX15 we sell is inspected and listed with its horsepower, ECM, and emissions rating, so you can match the right engine to your truck with confidence.
Need the right ISX15 for your truck? Send HD Engines your VIN or engine serial number, and our experts will help you confirm the correct specifications and find the right replacement. Call (786) 377-5210 or email info@hdengines.com to get started.