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. Learn more about intended use guidelines here.
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.
ISX12 G Walk-Around
ISX12 G Driver Familiarization
ISX12 G brochure
Natural Gas Driver Tips Card
Product Information Bulletin - Intended Use Guidelines
Product Information Bulletin - Spark Plug Cost Reduction
Product Information Bulletin - Altitude Specifications
|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.