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 p…
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 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.
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.
The most common questions about engine codes, what they mean, how to find them and how this database works
The N52 B25 B offers smooth performance and solid engineering, but early models (2005–2008) are prone to timing chain guide wear. Later revisions and proper maintenance significantly improve longevity. Regular cooling system service, use of correct oil (5W-30 BMW Longlife-01), and prompt attention to cold-start rattles are essential for reliability.
Key issues include timing chain guide wear (especially pre-2008), cooling system failures (thermostat, water pump), vacuum leaks from intake hoses, and oil leaks from valve cover and rear main seal. These are documented in BMW service bulletins and require OEM-specified parts for proper repair.
The N52 B25 B was used in the E90 3 Series 325i (2005–2011), E60 5 Series 525i (2005–2010), and E70 X5 3.0si (2006–2010). It was replaced by the N53B30 in 2011 with direct injection and updated engine management. No cross-manufacturer applications are documented for this variant.
Yes, though naturally aspirated. Stage 1 tuning includes ECU remap, high-flow intake, and performance exhaust, gaining ~15–25 kW. Cylinder head porting and camshaft upgrades offer further gains. Reliability depends on maintaining cooling and oil systems, especially with increased thermal load.
In an E90 325i, combined consumption is ~8.5 L/100km (33 mpg UK). City driving may see 10–11 L/100km (28–26 mpg), while highway cruising can achieve ~6.8 L/100km (41 mpg). Real-world figures depend on driving style and vehicle condition.
Yes. The N52 series is an interference engine. If the timing chain fails or jumps, pistons can contact open valves, causing severe internal damage. Chain maintenance and tensioner inspection are critical, especially given the engine's high-RPM operation.
BMW specifies 5W-30 synthetic oil meeting BMW Longlife-01 spec. Change intervals should not exceed 15,000 km. Proper oil ensures adequate protection for camshafts, lifters, and the timing chain, especially under sustained high-RPM use.
Comprehensive technical documentation and regulatory references
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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