Fuel dilution on D5 diesel - rising oil and runaway idle risk
SeriousEngineDVSA’s recall record for the S80 of this era states plainly that oil could rise above maximum from overfilling and/or fuel dilution, letting the engine hold or increase speed after the throttle is released and, in extreme cases, run on after switch-off. Owners' Club threads on the 2.0D/D5 cars show the day-to-day version: a rough, shaking idle where the members immediately suspect a leaking injector - at roughly £300 a time. Short urban runs made it a fleet-killer; verify oil history on any diesel you test.
Oil level above the maximum mark with a fuel smell, Rough idle with vibration through the floor, Engine reluctant to drop speed when pulled up, or running on after key-off
- Check the dipstick (level and smell) before the test drive
- Ask for proof of shortened oil-change intervals being honoured
- Run the plate through the DVSA recall service and confirm the fuel-dilution remedies are complete