The Cummins Westport ISX12 G natural gas engine is a larger-displacement natural gas engine suitable for a variety of heavy-duty vehicles, including regional-haul truck/tractor, vocational, and refuse applications. With a displacement of 11.9 liters and up to 400 hp and 1450 lb-ft of torque, the ISX12 G is the natural choice when considering alternative fuel for demanding applications. The ISX12 G operates on 100% natural gas which can be carried on the vehicle in either compressed (CNG) or liquefied (LNG) form. The ISL G can also run on renewable natural gas (RNG).
Featuring the same proven Stoichiometric cooled Exhaust Gas Recirculation (SEGR) combustion technology, spark ignition and simple Three-Way Catalyst (TWC) aftertreatment as the Cummins Westport ISL G engine, the ISX12 G delivers strong pulling power and heavy-duty durability and performance that customers can depend on.
For best reliability and durability, the recommended maximum GVW for line-haul applications is 80,000 lb (36,287 kg). Recommended gearing is 1400 rpm to 1475 rpm at cruise speed, to optimize fuel economy.
The ISX12 G meets current U.S. Environmental Protection Agency (EPA) and California Air Resource Board (ARB) emission standards and EPA greenhouse gas (GHG) and U.S. Department of Transportation (DOT) fuel consumption regulations.
|Advertised Horsepower||400 hp||298 kW|
|Peak Torque||1450 lb-ft||1966 N•m|
|Governed Speed||2,100 rpm|
|Clutch Engagement Torque||700 lb-ft||949 N•m|
|Type||4-cycle, spark-ignited, inline 6-cylinder, turbocharged, CAC|
|Displacement||726.2 cu. in.||11.9 L|
|Bore and Stroke||5.11 in x 5.91 in||130 mm x 150 mm|
|Oil System Capacity||12 U.S. gal||45.4 L|
|Coolant Capacity||26.5 U.S. qts||25.1 L|
|Net Weight w/ Std. Accessories, Dry||2,650 lbs||1.202 kg|
|Aftertreatment||Three-Way Catalyst (TWC)|
|Fuel Types||CNG / LNG / Biomethane
Methane number 75 or greater
|Availability||Click here for OEM availability|
Cummins Westport engines can accept a wide range of natural gas fuel compositions.
Use our Fuel Performance Specification Calculator to ensure compatibility.
|Engine Model||Advertised Horsepower
lb-ft (N•m) @ rpm
|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|
|ISX12 G 350R||350 (261)||1450 (1966) @ 1200||2100 rpm|
|ISX12 G 350R||350 (261)||1350 (1830) @1200||2100 rpm|
|ISX12 G 330R||330 (246)||1250 (1695) @ 1200||2100 rpm|
|ISX12 G 320R||320 (239)||1150 (1559) @ 1200||2100 rpm|
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. Natural gas engine oil should be CES 20074-approved. Cummins is requalifying its approved oils. A list of Cummins approved CES oils is available here. 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.
|Spin-on Fuel Filter||Daily Check|
|Oil And Filter*||25,000 mi (40,000 km)||500||6|
|Coolant Filter *||75,000 mi (120,000 km)||1,500||12|
|Spin-on Fuel Filter*||50,000 mi (80,000 km)||1,000||9|
|Spark Plugs*||75,000 mi (120,000 km)||1,500||12|
|Overhead Adjustment*||75,000 mi (120,000 km)||1,500||12|
|Engine Brake Adjustment||300,000 mi (480,000 km)||6,000||24|
|Standard Coolant||300,000 mi (480,000 km)||6,000||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. Spark Plug Cost reduction information here.
Watch a video overview of ISX12 G engine maintenance.