Cummins ISX12 G engine

ISX12 G (2013)

Power 320 - 400 hp
239 - 298 kW
Torque 1150 - 1450 lb-ft
1559 - 1966 N•m
Certification EPA 2013


Heavy-Duty Truck Natural Gas Engines

Available Regions

US and Canada,  Russia,  Africa & Middle East,  Mexico,  Philippines,  Singapore,  Brazil,  Bolivia,  Uruguay,  Paraguay,  Argentina,  Colombia,  Central America,  Europe,  Japan,  Korea


The ISX12 G natural gas engine delivers the strong pulling power and heavy-duty durability required for regional-haul truck/tractor, vocational and refuse applications. It features Stoichiometric cooled Exhaust Gas Recirculation (SEGR) combustion technology, which allows the use of a maintenance-free Three-Way Catalyst (TWC). Ratings range from 320 hp to 400 hp (239-298 kW) with 1450 lb-ft (1966 N•m) of peak torque. The inherent efficiency of this engine and an abundant supply of natural gas reduce operating costs, making the ISX12 G the natural choice for your fleet.

Dedicated Factory-Built Natural Gas Engine.
The ISX12 G is a dedicated, factory-built natural gas engine that is based on the Cummins ISX12 diesel engine. The ISX12 G shares many of the same parts and components as its diesel counterpart, and it operates on 100 percent clean-burning, low-cost natural gas. The ISX12 G meets current U.S. Environmental Protection Agency (EPA) and California Air Resource Board (ARB) emissions standards, and 2014 EPA greenhouse gas (GHG) and U.S. Department of Transportation (DOT) fuel consumption regulations.

The ISX12 G is a great choice for mixer, dump truck and refuse applications, with a high power-to-weight ratio and 700 lb-ft (949 N•m) of clutch engagement torque. Four refuse ratings, as well as Front Engine Power Take Off (FEPTO) and Rear Engine Power Take-Off (REPTO) options, offer power and flexibility for a wide variety of vehicles.

The ISX12 G is also the natural choice for regional-haul and LTL distribution operation trucks and tractors. Five ratings from 320 hp to 400 hp (239-298 kW), engine braking, and manual or automatic transmission capability provide trucking customers with the performance to meet fleet requirements, and the flexibility of using either compressed natural gas (CNG) or liquefied natural gas (LNG).

Advanced Combustion Technology.
The ISX12 G uses SEGR combustion with spark ignition to create a high-performance, heavy-duty natural gas engine. The cooled-EGR system takes a measured quantity of exhaust gas and passes it through a cooler to reduce temperatures before mixing it with fuel and the incoming air charge to the cylinder. SEGR results in improved power density and fuel economy versus traditional stoichiometric or lean-burn natural gas engines. This technology also enables the use of a TWC for emissions control.

Maintenance-Free Aftertreatment.
TWCs are effective, simple, passive devices packaged as part of the muffler. They provide consistent emissions control performance, are maintenance-free and can be mounted vertically or horizontally on the vehicle. The ISX12 G requires no active aftertreatment such as a Diesel Particulate Filter (DPF) or Selective Catalytic Reduction (SCR).

Natural Gas – The Fuel Choice Is Yours.
The ISX12 G operates on 100 percent natural gas, which can be carried on the vehicle in either compressed or liquefied form (CNG or LNG, respectively). The ISX12 G can also run on renewable natural gas (RNG) made from biogas or landfill gas that has been upgraded to vehicle fuel-quality. A variety of CNG and LNG tank configurations are available to meet range requirements. Consult your vehicle manufacturer for details.

Considering a Cummins engine purchase? For more information including pricing and additional technical information, please contact your Cummins representative. If you need help finding a representative, the Cummins Sales and Service Locator tool can help.

Maximum Horsepower 400 HP (298 kW)
Peak Torque 1450 LB-FT (1966 N•m)
Governed Speed 2100 RPM
Clutch Engagement Torque 700 LB-FT (949 N•m)

4-cycle, spark-ignited, in-line 6-cylinder, turbocharged, CAC

Engine Displacement 726.2 CU IN (11.9 LITERS)
Bore and Stroke 5.11 IN x 5.91 IN (130 MM x 150 MM)
Operating Cycles 4
Oil System Capacity 12 U.S. GALLONS (45.4 LITERS)
Coolant Capacity 26.5 U.S. QUARTS (25.1 LITERS)
System Voltage 12 V
Net Weight (Dry) 2,650 LB (1,202 kG)

Three-Way Catalyst (TWC)

Engine Model Advertised hp (kW) Peak Torque lb-ft (N•m) @ rpm Governed Speed
Line Haul Truck Applications      
ISX12 G 400 400 (298) 1450 (1966) @ 1200 2100 RPM
ISX12 G 385 385 (287) 1350 (1830) @ 1200 2100 RPM
ISX12 G 350 350 (261) 1450 (1966) @ 1200 2100 RPM
ISX12 G 330 330 (246) 1250 (1695) @ 1200

2100 RPM

ISX12 G 320 320 (239) 1150 (1559) @ 1200 2100 RPM
Refuse Truck Applications      
ISX12 G 350R 350 (261) 1350 (1830) @ 1200 2100 RPM
ISX12 G 350R 350 (261) 1450 (1966) @ 1200 2100 RPM
ISX12 G 330R 330 (246) 1250 (1695) @ 1200 2100 RPM
ISX12 G 320R 320 (239) 1150 (1559) @ 1200 2100 RPM
  • Advanced Air Handling – Electronic control for precise air handling.
  • Proven Wastegate Turbocharger – A small-frame, fixed geometry, waste gate-style turbocharger is used. A watercooled bearing housing adds durability.
  • Engine Control Module (ECM) – Constantly monitors and controls engine sensors, fuel system and ignition system. Drive-by-wire throttle control. Provides OEM and end users with the ability to tailor performance of the engine to fit the vehicle’s mission. Full interface capability to Cummins INSITE™ and Cummins QuickCheck diagnostic service tools.
  • High-Energy Ignition System – Provides better performance and longer service intervals, improved spark plug and coil durability and self-diagnostics. The ignition module and fuel module are controlled by a full-authority CM2180A ECM with programmable features, which is compatible with Cummins diagnostic tools.
  • Accessory Belt Drive System – Self-tensioning serpentine polyvee belt accessory drive system for water pump, engine-mounted fan hub and most alternators.
  • Air Intake System – Charge-air cooling reduces emissions by lowering intake manifold air temperatures.
  • High-Efficiency Lube Cooler – Lowers oil temperatures, for longer engine life.
  • Crankshaft – The eight-counterweight, fully balanced, high-tensile-strength steel forging has induction-hardened fillets and journals, for outstanding durability.
  • Optional Engine Braking – 240 hp (180 kW) at 2100 rpm.
  • Transmission – Automatic and manual options available.
  • Front- and Rear Engine Power Take-Off (FEPTO and REPTO) – Options provide additional torque, for a variety of vocational applications.

ISX12 G Torque Curves
ISX12 G Torque Curves
With torque curves similar to those of the ISX12 diesel within the 1150 lb-ft-to-1450 lb-ft (1559-1966 N•m) range, the ISX12 G offers comparable vehicle performance and drivability.

Gearing Recommendations
For best reliability and durability, the recommended maximum GVW for the ISX12 G in line-haul applications is 80,000 lbs (36,287 kg). Recommended gearing for line-haul applications is 1400 rpm to 1475 rpm at cruise speed for optimum fuel economy or 1450 rpm to 1500 rpm at cruise speed for a balance of fuel economy and performance. For vocational applications, gearing recommendations are 1450 rpm to 1600 rpm at cruise speed for fuel economy or 1550 rpm to 1700 rpm at cruise speed for a balance of fuel economy and performance.

Optimizing Performance with PowerSpec
Cummins PowerSpec helps you find the ideal gearing specs for engine performance or fuel economy, making it possible to tailor the operation of Cummins Westport engines to fit every customer’s application. PowerSpec can also read fault codes, and can be programmed to collect trip information for multiple drivers. PowerSpec works on both the ISL G and the ISX12 G. 

Base Warranty
The automotive base warranty for the Cummins Westport ISX12 G natural gas engine is the same as for the Cummins diesel base platform. Base warranty covers 2 years/250,000 miles (402,336 km) and 100 percent parts and labor on warrantable failures.*

Extended Coverage
For additional peace of mind, Cummins Westport offers a variety of extended coverage plans to meet every customer’s need. For details on extended coverage options, contact your local Cummins distributor or Cummins Westport representative.

Better Customer Care
Cummins Westport-powered vehicles are supported by Cummins service network, the largest and most capable in North America. Cummins authorized technicians are fully trained on Cummins Westport natural gas engines, with ready access to Genuine Cummins Parts and warranty support. For questions regarding your Cummins Westport engine, or for assistance in finding a repair facility in the United States or Canada, call Cummins Care at 1-800-CUMMINS.

Cummins Westport – The Natural Choice
Cummins Westport Inc. designs, engineers and markets 6- to 12-liter spark-ignited natural gas engines for commercial transportation applications such as trucks and buses. Our dedicated 100 percent natural gas engines are manufactured by Cummins, and are available as a factory-direct option from leading truck and bus manufacturers.

To learn more about Cummins Westport and natural gas as a transportation fuel, visit the Cummins Westport Natural Gas Academy for information, resources, videos and more – at

Overall, maintenance for the ISX12 G is similar to that of diesel engines, but there are a few key differences: 

Motor oil specifically formulated for natural gas engines is required.  Do not use diesel engine oil in a natural gas engine. If diesel engine oil is used, valve torching, piston scuffing and reduction in spark-plug life will occur. 

ISX12 G Maintenance Intervals - Line Haul Truck < 80,000 lb GVW

Maintenance Item Hours Distance Months
Spin-on Fuel Filter
Daily Check
Oil And Filter* 500 25,000 mi (40,000 km) 6
Coolant Filter * 1,500 75,000 mi (120,000 km) 12
Spin-on Fuel Filter* 1,000 50,000 mi (80,000 km) 9
Spark Plugs* 1,000 50,000 mi (80,000 km) 12
Overhead Adjustment* 3,000 150,000 mi (240,000 km) 24
Engine Brake Adjustment 6,000 300,000 mi (480,000 km) 24
Standard Coolant 6,000 300,000 mi (480,000 km) 24
Air cleaner / element Follow vehicle manufacturers published recommendations

* Assuming normal line haul duty cycle based on 50 mph /80 kph average speed.  Maintenance intervals must be reduced for slower average speed applications.  


ISX12 G Maintenance Intervals - Urban Truck / Refuse < 80,000 lb GVW



Maintenance Item^ Hours Distance Months
Oil and Filter* 500 7,500 mi (12,500 km) 6
Fuel Filter 1,000 15,000 mi (25,000 km) 9
Coolant Filter 1,500 22,500 mi (37,500 km) 12
Spark Plugs 1,000 15,000 mi (25,000 km) 12
Coolant Change 6,000 90,000 mi (150,000 km) 24
Overhead Adjustment** 3,000 45,000 mi (75,000 km) 24
Engine Brake Adjustment 6,000 90,000 mi (150,000 km) 24
Air Cleaner / Element Follow vehicle manufacturer's published recommendations

^Based on normal duty cycle of 15 mph / 25 kph average speed.  Distance intervals will increase or decrease based on average speed.
**Initial valve adjustment at 1,000 hours.
* Requires Natural Gas Engine Oil  - click here for more information.

Refer to QuickServe® Online or Owners Manual for complete details on maintenance intervals.




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