The 8.9 litre ISL G natural gas engine is North America’s natural choice for shuttle and school bus, urban transit, vocational and medium-duty truck and tractor natural gas applications. It 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.
The ISL G will save valuable fleet dollars through
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 GCVW for the ISL G in linehaul tractor applications is 66,000 lb (29,943 kg). Recommended gearing to optimize fuel economy is 1700 - 1800 rpm for linehaul applications, and 1750-1900 rpm for vocational applications.
To find out more about how using natural gas can improve your bottom line, contact your regional Cummins Westport sales representative.
Note: The ISL G is no longer available in North America. It has been replaced by the L9N—learn more here.
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 |
Aftertreatment | Three-Way Catalyst | |
Fuel Types | CNG / LNG / RNG Methane number 75 or greater |
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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 (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 |
Overall, maintenance for the ISL G is similar to that of diesel engines, but there are a few key differences:
An initial valve adjustment must be performed after 1,000 hours (15,000 miles/24,140 km) of operation, and is an important step in achieving longer engine life.
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 |
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 |
Cooling System Flush | 60,000 mi (96,000 km) | 2,000 | 24 |
Overhead Set Adjustment** | 60,000 mi (96,000 km) | 2,000 | 24 |
Ignition Coil Extension | 300,000 mi (480,000 km) | 10,000 | 5 yrs |
Air Cleaner / Element | Follow manufacturer's published recommendations | ||
^Based on a duty cycle of 30 mph / 48 kph average speed. Distance intervals will increase or decrease based on average speed. * Requires Natural Gas Engine Oil. For customers using CES 20092 natural gas engine oils only, the recommended interval is 1,000 hrs **Initial overhead set adjustment at 1,000 hours. |
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 |
Cooling System Flush | 30,000 mi (48,000 km) | 2,000 | 24 |
Overhead Set Adjustment** | 30,000 mi (48,000 km) | 2,000 | 24 |
Ignition Coil Extension | 150,000 mi (240,000 km) | 10,000 | 5 yrs |
Air Cleaner / Element | Follow manufacturer's published recommendations | ||
^Based on duty cycle of 15 mph / 25 kph average speed. Distance intervals will increase or decrease based on average speed. |
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.