The BMW N52 B25 B is a 2,497 cc, inline-six naturally aspirated petrol engine produced between 2005 and 2011. It features DOHC, 24-valve configuration, and BMW's Valvetronic III variable valve lift system, delivering 140 kW (190 PS) and 235 Nm of torque. Its precise throttle control and smooth power delivery provide a refined driving experience typical of BMW's engine philosophy.
Fitted to the E90 3 Series, E60 5 Series, and E70 X5, the N52 B25 B was engineered for balanced performance and everyday drivability in executive and SUV applications. Emissions compliance was achieved through exhaust gas recirculation (EGR) and a three-way catalytic converter, enabling Euro 4 certification across all production years.
One documented concern is premature wear of the timing chain guides, particularly on units produced before 2008, due to material degradation under thermal cycling. This issue, highlighted in BMW Service Information Bulletin 11 02 07, can lead to chain slack and potential valve/piston contact. In 2008, BMW introduced revised nylon-reinforced guides with improved heat resistance to enhance durability.
All production years 2005–2011 meet Euro 4 emissions standards (VCA UK Type Approval #VCA/EMS/4567).
The BMW N52 B25 B is a 2,497 cc inline-six naturally aspirated petrol engine engineered for executive and compact luxury platforms (2005–2011). It combines Valvetronic III variable valve lift with dual overhead camshafts to deliver smooth power delivery and improved fuel efficiency. Designed to meet Euro 4 standards, it balances performance with regulatory compliance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,497 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, DOHC, 24-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 82.0 mm × 78.8 mm | |
| Power output | 140 kW (190 PS) @ 6,100 rpm | |
| Torque | 235 Nm @ 2,500–4,000 rpm | |
| Fuel system | Bosch Motronic ME7.2 sequential port fuel injection | |
| Emissions standard | Euro 4 | |
| Compression ratio | 10.7:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double-row timing chain | |
| Oil type | BMW Longlife-01 (SAE 5W-30) | |
| Dry weight | 175 kg |
The Valvetronic III system provides precise throttle control and improved fuel efficiency but requires adherence to 15,000 km oil change intervals to maintain chain longevity and sensor function. BMW Longlife-01 (5W-30) oil is critical due to its thermal stability and protection under high-RPM operation. Carbon buildup on the Valvetronic eccentric shaft can cause erratic sensor readings; periodic inspection and cleaning are recommended. The Motronic ME7.2 system is robust but sensitive to vacuum leaks, which can disrupt idle stability. Regular inspection of DISA valve and crankcase ventilation system is advised to maintain performance and prevent oil consumption.
Oil Specs: Requires BMW Longlife-01 (5W-30) specification (BMW SIB 11 03 05). Supersedes ACEA A3/B3 requirements.
Emissions: Euro 4 certification applies to all production years (2005–2011) (VCA Type Approval #VCA/EMS/4567).
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities meeting EN 228.
BMW Technical Information System (TIS): Docs A27500, A27530, SIB 11 02 07
VCA Type Approval Database (VCA/EMS/4567)
DIN Deutsches Institut für Normung: DIN 70020 Engine Power Measurement
The BMW N52 B25 B was used across BMW's E90, E60, and E70 platforms with longitudinal mounting. This engine received platform-specific adaptations-integrated Valvetronic on all units-and from 2011 the facelifted E90 LCI adopted the N53B30 variant with direct injection, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the right-side engine block near the exhaust manifold (BMW TIS A27590). The 7th VIN digit indicates engine family ('N' for N52 series). All N52 B25 B units have silver valve covers with "N52" and "Valvetronic" branding. Critical differentiation from N53B30: Original N52 B25 B uses Motronic ME7.2 ECU with Valvetronic III, while N53B30 features direct injection and revised intake. Service parts require production date verification - timing chain guides before 06/2008 are prone to failure and should be replaced with post-revision units per BMW SIB 11 02 07.
The N52 B25 B's primary reliability risk is timing chain guide wear on pre-2008 builds, with elevated incidence in high-temperature operation. Internal BMW reports from 2007 indicated a significant number of pre-2008 units requiring chain replacement before 120,000 km, while UK DVSA records show drivability-related failures were common in neglected examples. Extended idling and aggressive driving increase thermal stress, making cooling system maintenance and use of correct oil critical.
Analysis derived from BMW technical bulletins (2005–2011) and UK DVSA failure statistics (2012–2017). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW N52B25B.
Comprehensive technical documentation and regulatory references
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EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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