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ISL G

The 8.9 litre ISL G heavy duty natural gas engine is North America’s natural choice to power for shuttle and school bus, urban transit, vocational and medium- and heavy-duty truck and tractor natural gas applications.  It meets 2013 U.S. Environmental Protection Agency (EPA) and California Air Resource Board (ARB) emission standards as well as the 2014 EPA and U.S. Department of Transportation (DOT) fuel economy and greenhouse gases regulations. 

The ISL G will save valuable fleet dollars through:

  • Lower fuel costs
  • Improved fuel economy
  • Lower total operating costs

First introduced in June 2007, the ISL 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).

For best reliability and durability, the recommended maximum GVW for the ISL G in linehaul tractor applications is 66,000 lb (29,943 kg). Recommended gearing for optimal cruise in linehaul appilcations is 1600-1900 rpm. For vocational applications,
the recommended gearing is 1800-2100 rpm.

To find out more about how using natural gas can improve your bottom line, contact your regional Cummins Westport sales representative. 

Click to see a walk-around video of the ISL G.

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Advertised Horsepower 320 hp 239 kW
Peak Torque 1,000 lb-ft 1,356 N•m
Governed Speed 2,200 rpm
Clutch Engagement Torque 550 lb-ft 746 N•m
Type 4-cycle, spark-ignited, inline 6-cylinder, turbocharged, CAC
Displacement 540 cu. in. 8.9 L
Bore and Stroke 4.49 in x 5.69 in 114 mm x 145 mm
Operating Cycles 4
Oil System Capacity 7.3 U.S. gal 27.6 L
Coolant Capacity 13.1 U.S. qts 12.4 L
System Voltage 12 V
Net Weight w/ Std. Accessories, Dry 1,625 lbs 737 kg
Fuel Types CNG / LNG / Biomethane
Methane number 75 or greater
Aftertreatment Three-Way Catalyst (TWC)

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
(kW) @ rpm		 Peak Torque 
lb-ft (N•m) @ rpm		 Governed
Speed
ISL G 320 320 (239) @ 2000 1000 (1356) @ 1300 2200 rpm
ISL G 300  300 (224) @ 2100 860 (1166) @ 1300 2200 rpm
ISL G 280 280 (209) @ 2000 900 (1220) @ 1300 2200 rpm
ISL G 260 260 (194) @ 2200 660 (895) @ 1300 2200 rpm
ISL G 250  250 (186) @ 2200 730 (990) @ 1300 2200 rpm

ISL G Truck < 66,000 GVW

Maintenance Item Distance Hours Months
Oil and Filter* 15,000 mi (24,000 km) 500 6
Fuel Filter 30,000 mi (48,000 km) 1,000 12
Coolant Filter 15,000 mi (24,000 km) 500 6
Spark Plugs 45,000 mi (72,000 km) 1,500 18
Coolant Change 60,000 mi (96,000 km) 2,000 24
Valve Adjustment** 60,000 mi (96,000 km) 2,000 24
* Requires Natural Gas Engine Oil (CES20074). Click here for more information.
**Initial valve adjustment at 1,000 hours.

ISL G Urban Transit Bus

Maintenance Item Distance Hours Months
Oil and Filter* 7,500 mi (12,000 km) 500 6
Fuel Filter 15,000 mi (24,000 km) 1,000 12
Coolant Filter 7,500 mi (12,000 km) 500 6
Spark Plugs 22,500 mi (36,000 km) 1,500 18
Coolant Change 30,000 mi (48,000 km) 2,000 24
Valve Adjustment** 30,000 mi (48,000 km) 2,000 24
* Requires Natural Gas Engine Oil (Cummins Engineering Standards  20074).   Click here for more information.
**Initial valve adjustment at 1,000 hours.
  • Default interval is the hours stated. Interval is whichever comes first – hours, miles or time.
  • Refer to quickServe® Online or Owners Manual for complete details on maintenance intervals.

Factory-Built, Dedicated Natural Gas Engine – Manufactured on the same assembly line as Cummins diesels, the ISL G shares many components and parts with Cummins L Series diesels, inheriting their renowned simplicity.

  • Electronic Control Module: Provides full monitoring and control of engine sensors, fuel system and ignition system, with full interface capability to Cummins INSITE and diagnostic service tools.
  • Three-Way Catalyst: Simple passive device, highly effective hydrocarbon, CO and NOx control with no maintenance costs.  .  No Diesel Particulate Filter (DPF) or Selective Catalytic Reduction (SCR) systems are required
  • Low installed weight: Highest power:weight ratio in its class.
  • High-Energy Ignition System –Better performance and longer service intervals and improved spark plug and coil durability, plus self-diagnostics.
  • Fuel Capability - Natural gas can be stored on the vehicle in either compressed (CNG) or liquefied (LNG) form. The ISL G can also operate on renewable natural gas or biomethane that meets fuel-quality specifications.
  • Meets EPA and CARB 2010 and Euro EEV emission standards
  • #1 OEM Available Natural Gas Engine - Available as a factory built option from all leading truck and bus builders in North America; the ISL G is the natural choice