Product Description
Cummins 4089181 — Piston Ring Set (.020" / 0.50 mm Oversize)
MPN: 4089181 | Also Known As: overbore piston rings, 0.50 mm O/S ring set | Cross-Refs (ID only): 3949579, 3957244; kit components commonly include 3933585 (oil ring) & 3943545 (compression ring)
Why This Part
- ✓ OE ring pack for proper sealing, compression, and oil control after machine overbore.
- ✓ .020" (0.50 mm) oversize for cylinders bored/honed beyond standard.
- ✓ Direct-fit for ISB applications when matched to the correct piston/bore.
- ✓ Durable materials engineered to OE spec for long service life.
Quick Specs
| Type | Piston ring set (overbore) |
|---|---|
| Oversize | 0.50 mm (.020") |
| OE Part # | 4089181 |
| Packaging | Sold as a ring set for one cylinder/piston (order 6 for a full 6-cyl engine) |
Verified Fitment (Automotive)
| Year Range | Engine | Chassis |
|---|---|---|
| 2003–2007 | Ram 5.9L ISB (24V Common-Rail) — .020" overbore required | Ram 2500/3500 |
Industrial/Off-Highway: Common on ISB/QSB applications (incl. 3.9L/4.5L) in Tier 2/3 variants — always confirm by ESN and piston/bore spec.
Often Paired With
- Matching .020" over pistons for your ESN/CPL (OE or performance)
- Head gasket set and upper engine kit for refresh
- Honing/boring services and ring compressor tool
- Fresh oil & filter after break-in
What’s In The Box
- (1) Genuine Cummins .020" (0.50 mm) Piston Ring Set — typically for one cylinder
- Other engine components sold separately
Install Tips
- Confirm piston design & ring groove specs match this ring set before machining.
- Measure final bore; set ring end-gaps to spec and stagger ring openings.
- Clean bores thoroughly after honing; oil cylinders and rings at assembly.
FAQ
WILL THIS FIT MY 2003–2007 5.9L CUMMINS RAM?Yes—this .020" oversize ring set is listed for 2003–2007 5.9L ISB (verify by VIN/ESN and piston/bore spec).
IS THIS .020" OVER (0.50 MM) AND DOES MY BLOCK NEED MACHINING?Yes—4089181 is a 0.50 mm (.020") oversize ring set and requires an overbored/honed cylinder.
HOW MANY SETS DO I NEED FOR A FULL ENGINE?This ring set is typically packaged per cylinder. For a 6-cylinder engine, order quantity 6.
DO I NEED MATCHING OVERSIZE PISTONS?Yes—rings must match piston/ring groove design and the finished bore size. Use .020" over pistons with this ring set.
IS THIS A GENUINE CUMMINS PART?Yes—OE Cummins part 4089181.
