ISB6.7 G

In 2016, Cummins Westport introduced a new dedicated natural gas engine for school bus, shuttle, transit, medium-duty truck, and vocational vehicle markets. Based on the Cummins ISB6.7 diesel platform, the Cummins Westport ISB6.7 G offers up to 240 hp (179kW) and 560 lb-ft (759 Nm) of torque, and is available with automatic transmissions. Not only does the ISB6.7 G meet U.S. Environmental Protection Agency (EPA) and California Air Resources Board (ARB) 2016 emissions regulations, it also meets ARB's optional low oxides of nitrogen (NOx) standard of 0.1 g/bhp-hr, and it meets 2017 EPA greenhouse gas (GHG) requirements a year ahead of schedule.

The ISB6.7 G features the same advanced combustion controls with Three-Way Catalyst (TWC) as Cummins Westport’s ISL G & ISX12 G engines. It operates on 100 percent natural gas, which can be carried on the vehicle in either compressed or liquefied form (CNG / LNG respectively). It can also run on 100 percent biomethane
or renewable natural gas, which meets published Cummins fuel specifications.

Note: The ISB6.7 G is no longer available. It has been replaced by the B6.7N—learn more here.

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Advertised Horsepower 240 hp 179 kW
Peak Torque 560 lb-ft 759 N•m
Governed Speed 2,630 rpm
Type 4-cycle, spark-ignited, inline 6-cylinder, turbocharged, CAC
Displacement 409 cu. in. 6.7 L
Operating Cycles 4
Aftertreatment Three-Way Catalyst
Fuel Types CNG / LNG / RNG
Engine Model Advertised Horsepower
(kW) @ rpm
Peak Torque 
lb-ft (N•m) @ rpm
ISB6.7 G 200 200 (149) @ 2400 520 (705) @ 1600 2600 rpm
ISB6.7 G 220 220 (164) @ 2400 520 (705) @ 1600  2600 rpm
ISB6.7 G 240 240 (179) @ 2400 560 (759) @ 1600  2600 rpm


ISB6.7 G < 33,000 GVW

Overall, maintenance for the ISB6.7 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. 
  • For more information, see the links below or visit Cummins QuickServe Online.
Maintenance Item Distance Hours Months
Check CAC cooler, piping, and Air cleaner 7,500 mi (12,000 km) 250 3
Oil and Filter* 15,000 mi (24,000 km) 500 6
Spin-On Fuel Filter 30,000 mi (48,000 km) 1,000 9
Spark Plugs 25,000 mi (40,000 km) 750 9
Overhead Adjustment 45,000 mi (72,000 km) 1,500 12
Standard Coolant 60,000 mi (96,000 km) 2,000 24
Crankcase Ventilation Filter 60,000 mi (96,000 km) 2,000 24
Ignition Coil Extension 150,000 mi (240,000 km) 5,000 5 yrs
Air Cleaner / Element Follow manufacturer's published recommendations

* Requires Natural Gas Engine Oil.

  • Default interval is the hours stated. Interval is whichever comes first – hours, miles or time.
  • Based on a normal duty cycle of 30 mph average speed.  Distance intervals will increase or decrease based on average speed.
  • Refer to QuickServe Online or Owners Manual for complete details on maintenance intervals.
  • Advanced Combustion Technology – The ISB6.7 G uses the same Stoichiometric cooled Exhaust Gas Recirculation (SEGR) combustion technology, spark ignition, and simple TWC aftertreatment as the ISL G and ISX12 G natural gas engines. 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 and enables the use of a TWC for emissions control
  • Three-Way Catalyst Aftertreatment – Three-Way Catalysts (TWCs) are effective, simple devices, packaged as part of the muffler, that provide consistent emissions control performance and are maintenance-free.  No Diesel Particulate Filter (DPF) or Selective Catalytic Reduction (SCR) systems are required.
  • Proven Design – The ISB6.7 G shares many base engine components with the ISB6.7 diesel engine and shares the emissions architecture of the ISL G and ISX12 G, including wastegate turbocharger, a high-energy ignition system controlled by the CM2180A Engine Control Module, and similar fuel module design.
  • Fuel Capability – Natural gas can be stored on the vehicle in either compressed (CNG) or liquefied (LNG) form. The ISB6.7G can also operate on renewable natural gas or biomethane that meets fuel-quality specifications.