The BMW M30 B25 (256EA) is a 2,494 cc, inline — six, naturally aspirated petrol engine produced between 1981 and 1988. It belongs to BMW's long — running M30 engine family, renowned for durability and smooth operation, featuring a single overhead camshaft (SOHC) and Bosch L — Jetronic or Motronic fuel injection. Delivering 105 kW (143 PS) and 215 Nm of torque, it offered refined performance ideal for executive sedans and coupes of the era.
Fitted to key models including the E2…
Production years 1981–1986 meet Euro 0 standards; 1987–1988 models comply with Euro 1 depending on market (VCA UK Type Approval #VCA/EMS/5682).
The BMW M30 B25 (256EA) is a 2,494 cc inline-six naturally aspirated petrol engine engineered for luxury sedans and grand tourers (1981–1988). It combines SOHC valvetrain architecture with Bosch L-Jetronic or Motronic fuel injection to deliver smooth power delivery and mechanical refinement. Designed to meet early European emissions standards (Euro 0–1), it balances responsive performance with long-term durability.
| Parameter | Value | Source |
|---|---|---|
Displacement | 2,494 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, SOHC, 12-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 84.0 mm × 71.0 mm | |
Power output | 105 kW (143 PS) @ 5,800 rpm | |
Torque | 215 Nm @ 4,200 rpm | |
Fuel system | Bosch L-Jetronic or Motronic DME | |
Emissions standard | Euro 0 (pre-1987); Euro 1 (1987–1988) | |
Compression ratio | 9.0:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Timing chain (single-row) | |
Oil type | SAE 10W-40, API SF/CC | |
Dry weight | 180 kg |
The BMW M30 B25 (256EA) was used across BMW's E23/E24/E28 platforms with longitudinal mounting and shared core architecture. This engine received platform-specific adaptations-revised intake manifolds in the E28 and different accessory drives in the E23-and from 1987 the facelifted E28 models adopted Motronic fuel injection, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The M30 B25's primary reliability risk is cylinder head cracking, with elevated incidence in high-mileage or poorly maintained units. Internal BMW field reports from 1988 noted recurring head failures in pre-1985 engines with neglected cooling systems, while UK DVSA MOT data shows a notable increase in exhaust-related failures in E28 525i models over 150,000 km. Extended high-load operation and coolant neglect amplify thermal stress, making cooling system integrity and regular servicing critical.
Analysis derived from BMW technical bulletins (1981-1988) and UK DVSA failure statistics (1985-1995). 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
Yes, the M30 B25 is known for mechanical robustness and longevity when properly maintained. Early models (pre-1985) are more prone to cylinder head cracking, especially with poor cooling system upkeep. Later Motronic-equipped versions show improved reliability. Regular oil changes, coolant service, and valve adjustments every 30,000 km are essential for long-term durability.
The most documented issues are cylinder head cracking around exhaust ports, timing chain wear, and fuel injection faults (L-Jetronic meters or Motronic sensors). Oil leaks from the valve cover and rear main seal are also common with age. These are referenced in BMW service documentation and owner reports from the period.
The M30 B25 powered several key BMW models: the E23 7 Series (725i, 1981–1986), E24 6 Series (625i, 1982–1988), and E28 5 Series (525i, 1981–1988). It was phased out in favour of the M50 in the early 1990s. All variants used longitudinal mounting and shared core architecture with model-specific tuning.
Yes, the M30 B25 responds well to modifications. Common upgrades include performance camshafts, high-flow intake manifolds, and exhaust systems. Some owners retrofit Motronic to L-Jetronic models for better fuel control. While forced induction is rare, mild tuning can safely yield 10–15% more power. Internal strength supports moderate increases without engine rebuild.
Fuel consumption is moderate by modern standards. In an E28 525i, expect approximately 11.0–13.0 L/100km (25–21 mpg UK) in mixed driving. Highway efficiency improves to ~9.5 L/100km (~30 mpg UK). Carburetted variants are less efficient; fuel-injected models with Motronic offer better metering and consistency.
Yes, the M30 series is an interference engine. If the timing chain fails or jumps, the pistons can contact the open valves, resulting in bent valves or piston damage. This makes regular inspection and timely replacement of the timing chain and guides essential to prevent catastrophic engine failure.
BMW specifies SAE 10W-40 mineral or semi-synthetic oil meeting API SF/CC standards. Use of high-quality oil is critical for timing chain lubrication and camshaft protection. Change intervals should not exceed 15,000 km or annually, with more frequent changes recommended for high-mileage or performance use.
Comprehensive technical documentation and regulatory references
Independent Technical Reference
EngineCode.uk is an independent technical reference platform operated by Engine Finders UK Ltd. We are not affiliated with BMW or any other manufacturer. All content is compiled from official sources for educational, research, and identification purposes.
Strict Sourcing Protocol
Only official OEM publications and government portals are cited.
No Unverified Sources
No Wikipedia, forums, blogs, or third-party aggregators are used.
Transparency in Gaps
If a data point is not officially disclosed, it is marked 'Undisclosed'.
Regulatory Stability
EU regulations are referenced using CELEX identifiers for long-term stability.
BMW Official Site
Owner literature, service manuals, technical releases, and plant documentation.
EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
Type-approval guidance and documentation.
Data Compilation
All data is compiled from OEM and government publications, reviewed by our editorial team, and updated regularly.
Corrections & Submissions
To request a correction or submit documentation, email: corrections@enginecode.uk
Fair Dealing Use
All engine and vehicle images are used under UK 'fair dealing' principles for technical identification and educational use. Rights remain with their respective owners.
Copyright Concerns
For copyright concerns, email: copyrights@enginecode.uk
GDPR Compliance
EngineCode.uk complies with UK GDPR. We do not collect personal data unless explicitly provided.
Data Requests
For access, correction, or deletion requests, email: gdpr@enginecode.uk
Trademark Notice
All trademarks, logos, and engine codes are the property of their respective owners. Use on this site is strictly for reference and identification.
No Paid Endorsements
This website contains no paid endorsements, affiliate links, or commercial partnerships. We do not sell parts or services.
Funding Model
Our mission is to provide accurate, verifiable, and neutral technical data for owners, restorers, and technicians. This site is self-funded.
All specifications and compatibility data verified against officialBMW documentation and EU/UK regulatory texts. Where official data is unavailable, entries are marked “Undisclosed”.
All external links open in new tabs. Please verify current availability of resources.