The Cummins/Onan QSJ5.9G is a 5.88 L 6-cylinder naturally aspirated or turbocharged (varies by generator set model) engine rated at 1800 rpm. It powers generator sets from Cummins/Onan, including the C100 N6, C45 N6, C50 N6 and C60 N6. It holds 15.1 L (4.0 gal) of oil and 16 L (4.2 gal) of coolant.
Maintenance schedule
| Item | Spec | Capacity | Part # | Interval | |
|---|
| Air filter | Replace air cleaner. | | — | 250 hr | |
| Fuel filter | Check fuel lines and hoses: Visually check for leaks, worn or damaged hoses. To replace, contact your authorized distributor. | | — | 24 hr | |
| Oil filter | Replace engine oil and filters. Refer to the Engine Oil section for the procedure. | | — | 250 hr | |
| Battery | Check battery: Check connections to verify that they are secure. | | — | 50 hr | |
| Belt | Checking drive belt condition and tension: Visually check belt for evidence of wear or slippage. To replace, contact your authorized distributor. | | — | 24 hr | |
| Coolant | Replace cooling system coolant. Check coolant sensor for damage and debris. | | — | 500 hr | |
| Oil | Replace engine oil and filters. Refer to the Engine Oil section for the procedure. | | — | 250 hr | |
| Spark plug | Replace spark plugs and spark plug wires. | | — | 500 hr | |
Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.
Parts cataloged across the Cummins/Onan QSJ5.9G family
4| Part # | Description | Category |
|---|
| 3824510 | Cummins electronic cleaner | other_service |
| A047A982 | EControls GCP E-Com USB interface cable | other_service |
| A026M166 | accessory seal kit | seal |
| B180313494 | Onan C50N6 March Inspection | service_type |
Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.
Common questions
What is the oil capacity of the Cummins/Onan QSJ5.9G?
The Cummins/Onan QSJ5.9G engine has an oil capacity of 15.1 liters.
What is the displacement of the Cummins/Onan QSJ5.9G?
The Cummins/Onan QSJ5.9G has a displacement of 5.88 liters with 6 cylinders.
Which generators use the Cummins/Onan QSJ5.9G engine?
The Cummins/Onan QSJ5.9G powers 6 generator set(s), including Cummins/Onan C100 N6, Cummins/Onan C45 N6, Cummins/Onan C50 N6, Cummins/Onan C60 N6, Cummins/Onan C70 N6.
How often should you change the oil in the Cummins/Onan QSJ5.9G?
The Cummins/Onan QSJ5.9G oil change interval is every 250 hours.
What is a common problem with the Cummins/Onan QSJ5.9G engine?
A commonly reported issue on generators using the Cummins/Onan QSJ5.9G is: Unknown Shutdown at Idle.