N55B30

1 Series·F20·2015–2016·2,979 cc

"For the N55, just about no complaints — short term reliability is fine."

SOLID

71/ 100

"Strong six, but watch the chain"

493

Max HP

680

Torque Nm

10,000

Oil interval km

Recalls

Known issues

Known Issues

Timing Chain Guide Wear & Failure€1,500-3,500 · 80,000-160,000 kmHIGH

Plastic timing chain guides are known to crack and shed fragments into the oil sump. The N55 shares a family-level vulnerability with other BMW inline engines of this era. Plastic debris found in the sump is a confirmed sign the job can no longer be deferred. Dealers have reported difficulty achieving correct timing after replacement, requiring skilled labor.

Rattling noise from engine on cold start

Plastic debris or sludge in oil sump on inspection

Check engine light with timing-related fault codes

Rough idle or misfires at startup

DIY: Expert

Rod Bearing Failure (Spun Bearing)€3,000-8,000 · 100,000-200,000 kmHIGH

Spun rod bearings have been reported on the N55, consistent with the broader BMW N-series inline-six family. Engine builders specifically advise against attempting crank repair and recommend sourcing a replacement long block instead, indicating the severity and cost of this failure.

Loud knocking or ticking from bottom end

Sudden loss of oil pressure

Engine failure or seizure

DIY: Expert

EGR Cooler Leak€400-1,200 · 80,000-150,000 kmMODERATE

EGR cooler leaks have been flagged in a DVSA recall covering nearly 35,000 BMW and MINI vehicles. The EGR cooler is mounted directly to the exhaust manifold. Replacement is described as relatively accessible once intake tubing is removed.

Coolant loss without visible external leak

White smoke or sweet smell from exhaust

Overheating or coolant warning light

DIY: Moderate

High Operating Temperature Sensitivity€0-500 · 0-999,999 kmMODERATE

BMW N-series engines are intentionally engineered to run at elevated temperatures to meet Euro emissions standards and improve turbo efficiency. This places greater demands on coolant system maintenance, thermostat condition, and oil quality. Neglected cooling systems accelerate other failure modes.

Temperature gauge running higher than expected

Increased coolant consumption

Thermostat or water pump failures

DIY: Moderate

Buying Checklist

Pull full service history — confirm oil changes every 10,000 km or less with correct BMW LL spec oil

Perform cold-start test and listen carefully for timing chain rattle from the front of the engine

Request an oil sump inspection or recent oil sample analysis to check for plastic timing guide debris or metal particles

Verify EGR cooler recall completion by running the VIN through the DVSA or BMW recall checker before purchase

Check coolant level, colour, and condition — inspect for any signs of leaks around the EGR cooler and water pump area

Scan all ECU modules for fault codes, particularly any timing chain correlation errors, oil pressure faults, or boost-related codes

Service Reality

Community oil interval10,000 km

Oil specificationBMW Longlife-01 or LL-04 compliant 5W-30 fully synthetic

Est. ownership cost (2yr)€1,200–2,500 per year depending on mileage, with a potential €1,500–3,500 timing chain service required in the 80,000–130,000 km window

Real mix fuel consumptionNo data

Also Found In

BMW 335i (F30/F31/F34)BMW 535i (F10/F11)BMW 135i (F20/F21)BMW 435i (F32/F33/F36)BMW X3 xDrive35i (F25)BMW X4 xDrive35i (F26)BMW Z4 sDrive35i (E89)BMW 640i (F06/F12/F13)

Buying Advice

The N55B30 in the F20 LCI is a genuinely capable and rewarding inline-six, but it rewards disciplined maintenance above all else. Prioritise cars with verifiable short-interval oil change history, as neglect accelerates both timing chain guide wear and rod bearing risk. Always perform a cold-start inspection and confirm the EGR recall has been completed before committing. Budget for proactive timing chain service if the vehicle is approaching 100,000 km without documented chain work — catching it early is far cheaper than an engine rebuild.