Cummins/Onan QSB4.5 Engine
The Cummins/Onan QSB4.5 is a 4.5 L 4-cylinder turbocharged and charge-air cooled engine rated at 1470 rpm, producing up to 78 kW. It powers generator sets from Cummins/Onan, including the CFP5E-F10, CFP5E-F20, CFP5E-F40 and CFP5EVS-F10. It holds 11.6 L (3.1 gal) of oil and 13 L (3.4 gal) of coolant.
Also known as: Cummins QSB4.5
Part of the Cummins/Onan QSB4.5 engine family — 2 variants share parts & fitment.
Engine specifications
| Oil capacity | 11.6 L |
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| Coolant capacity | 13.0 L |
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| Displacement | 4.5 L |
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| Cylinders | 4 |
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| Aspiration | Turbocharged and Charge-Air Cooled |
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| Rated speed | 1470 rpm |
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| Gross power | 78 kW |
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Maintenance schedule
| Item | Spec | Capacity | Part # | Interval | |
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| Fuel filter | Recommended fuel filter - primary Cummins Filtration FF5612 (Cummins 4989106); secondary element AF26125 | | — | | |
| Oil filter | Recommended lube oil filter - Cummins Filtration LF3970 | | LF3970 | | Amazon eBay $177.58 NAPA $22.00 FridayParts $62.99 |
| Battery | Battery cable size - minimum of 2/0 AWG and maximum cable length not to exceed 6 ft. (1.5 m) | | — | | |
| Belt | Exhaust protection - Metal guards on manifolds and turbocharger; Exhaust flex connection - Steel, flanged; Stainless steel flex, NPT | | — | | |
| Coolant | Cooling system - Tube and shell type, 60 PSI with NPTF connections; recommended minimum water supply pipe size to heat exchanger .75 in. (19.05 mm); recommended minimum water discharge pipe size from heat exchanger 1.00 in. (25.40 mm) | | — | | |
| Oil | Oil capacity of pan (high - low) 11.6-9.5 qt. (11-9 L) | 11.0 qt,L | — | | |
| Spark plug | Engine only - cold cranking amperes: 1300 CCA*; Engine only - reserve capacity: 430 minutes* | | — | | |
Pooled from every document that names this exact engine — confirm the interval and part number against your unit's serial number.
Service intervals
5| Item | Action | Hours | Months | Notes |
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| Lubricating oil | Test | 250 hr | 6 mo | First service — For high horsepower engines with Eliminator™ oil filter option: take oil samples every 250 hours and analyze per Cummins Engine Oil Recommendations Bulletin 3810340; repeat for at least three oil change intervals. |
| filters | Change | 1000 hr | | with CENTINEL, depending on load factors |
| ELIMINATOR self cleaning filter core | Other | 1500 hr | | Requires servicing only every 1,500 hours. Saves up to 90% of lube system maintenance costs and increases productivity. |
| fuel filter | Change | 1500 hr | | Fleetguard NanoNet media |
| engine oil | Change | 4500 hr | | with CENTINEL, railway applications |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Service specifications
4| Type | Item | Value | Unit | Condition |
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| Other | Pressure sensing line nominal size inside diameter | 1/2 | in. (12.7 mm) | connected between the transducer (located under the FPDP) and the pump discharge flange and the discharge check valve |
| Pressure | Cooling loop cooling water pressure limit | 270 | psi | installations where the discharge pressure is greater than 270 psi (pressure reducing valve required upstream of the cooling loop) |
| Pressure | Discharge set point pressure / maximum control pressure | 100/110, 170/175, or 240/250 | psi | set by the factory and not adjustable; specify at time of order |
| Pressure | VSPLC set point range | 100 to 400 | psi | |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Recommended fluids
| Fluid | Grade | Standard | Ambient | Capacity | Notes |
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| Engine oil | | Cummins Engine Oil Recommendations Bulletin 3810340 | | | Used to analyze oil samples for high horsepower engines with Eliminator™ oil filter option. |
| Fuel | B100 biodiesel | ASTM D6751 | | | Must conform prior to blending; revised to include a cold soak test; stability requirement still in effect. |
| Fuel | B20 biodiesel blend | ASTM D7467 | | | Applies to biodiesel blends B6–B20; includes oxidation stability requirement; replaces Cummins' previous EMA B20 specification requirement. Must be purchased from a BQ9000 Certified Marketer; B100 must be sourced from a BQ9000 Accredited Producer. |
| Fuel | B5 biodiesel | | | | All Cummins automotive and industrial engines are compatible with B5 biodiesel. |
| Fuel | biodiesel (Europe) | EN 14214 | | | Published by CEN, European Committee for Standardization. Equivalent biodiesel specifications required internationally. |
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Procedures
2Oil sampling for high horsepower engines with Eliminator™ oil filter option maintenance
- Take oil samples every 250 hours of operation.
- Analyze samples according to Cummins Engine Oil Recommendations Bulletin 3810340.
- Repeat for at least three oil change intervals to ensure consistent oil behavior.
Switching from petrodiesel to B20 on used engines maintenance
⚠ B20 has a solvent nature and may clean the vehicle fuel tank and lines.
- Install new fuel filters when switching to B20.
- Replace fuel filters at half the standard interval for the next two fuel filter changes.
- After the initial period, revert to intervals specified in the O & M manual.
- For EPA 2007 on-highway midrange engines, sample oil for the first 6 months to monitor fuel dilution.
Extracted from the manufacturer documentation linked to this model. Values are copied as printed; confirm against your unit's manual and serial number.
Parts cataloged across the Cummins/Onan QSB4.5 family
2| Part # | Description | Category |
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| CC900G | Parking brakes, Horn, Hour meter, Ignition key, Propulsion in both drums, Foldable ROPS (incl. seat belt), Seat safety switch, Sliding operator seat, Towing eyelet (front/rear), Vibration on front drum, Cup Holders, Carbon Canister, Fuel Level gauge | Belt |
| CC950 | Emergency stop, Horn, Hour meter, Ignition key, Propulsion in both drums, Foldable ROPS (incl. seat belt), Seat safety switch, Sliding operator seat, Towing eyelet (front/rear), Vibration on front drum, Warning light for brakes, Cup Holders, Low Fuel level meter, LED working lights | Belt |
Parts cataloged across all variants of this engine family — verify the exact part fits your specific variant and serial number before ordering.
Aftermarket parts that fit this engine
2Parts listed by aftermarket suppliers as fitting this engine — leads compiled from supplier catalogs; verify the exact part for your serial number.
Common questions
What is the oil capacity of the Cummins/Onan QSB4.5?
The Cummins/Onan QSB4.5 engine has an oil capacity of 11.6 liters.
What is the displacement of the Cummins/Onan QSB4.5?
The Cummins/Onan QSB4.5 has a displacement of 4.5 liters with 4 cylinders.
Which generators use the Cummins/Onan QSB4.5 engine?
The Cummins/Onan QSB4.5 powers 7 generator set(s), including Cummins/Onan CFP5E-F10, Cummins/Onan CFP5E-F20, Cummins/Onan CFP5E-F40, Cummins/Onan CFP5EVS-F10, Cummins/Onan CFP5EVS-F20.