Piston cracking from fuel dilution
Attaches to N22B at engine level · Engine · carried by 2 variants across 2 chassis
Overview
Piston cracking from fuel dilution is a occasional fault recorded against N22B at engine level, typically from 100–200k km. It shows up as rising oil level with a diesel smell, rough running, and at worst a knock and loss of compression. Where it's documented, the repair runs €2,500–€5,000 (engine repair or replacement at a specialist, costs dated 2026-07), and it can be partly checked before you buy. 2 variants across 2 chassis in this database inherit it.
What happens
Symptom. Rising oil level with a diesel smell, rough running, and at worst a knock and loss of compression.
Cause. Repeated incomplete particulate-filter regenerations wash unburnt fuel past the rings and dilute the oil. On short-trip cars this eventually damages a piston. Cars used for longer journeys largely escape it, so how the car was driven matters more than the mileage.
How to check it
Paperwork
Check the oil level and smell it for diesel, ask directly what journeys the car did, and read the service record for short intervals or repeated top-ups.
On these cars the folder is most of the value.
Every variant that carries this
| Variant | Chassis | Body | Years | Risk | Good buy | Cost as % of good buy |
|---|---|---|---|---|---|---|
| 2.2 i-DTEC N22B | CU | sedan | 2008–2015 | R4 | €2,600 | 144% |
| 2.2 i-DTEC N22B | CW | wagon | 2008–2015 | R4 | €2,700 | 139% |
The last column is the point. The same repair is an inconvenience on one variant and a reason to scrap the car on another. A failure costing a quarter of the vehicle's value changes the purchase decision regardless of how rare it is.