The BMW M10 B15 is a 1,499 cc, inline-four naturally aspirated petrol engine produced between 1975 and 1984.
It is a member of BMW's long-running M10 engine family, one of the most durable and widely used powerplants in the brand's history.
Featuring a single overhead camshaft (SOHC), 8-valve configuration, and carbureted fuel delivery (Solex 32-32 DIDTA or Pierburg 2E3), it produces 63 kW (86 PS) at 6,000 rpm with peak torque of 125 Nm at 4,500 rpm.
Designed for reliability and ease of maintenance, the M10 B15 was used in entry-level BMW sedans and coupes during the 1970s and early 1980s, forming the base engine for the 3 Series (E21) lineup.
Pre-1980 engines meet Euro 1 standards; later units comply with early Euro 2 regulations (VCA Type Approval #VCA/EMS/1029).
The BMW M10 B15 is a 1,499 cc inline-four naturally aspirated petrol engine engineered for longitudinal-mounted rear-wheel-drive vehicles (1975–1984). It combines a simple SOHC valvetrain with carburetion to deliver smooth, predictable performance. Designed before the era of electronic fuel injection, it prioritizes mechanical simplicity and serviceability over high specific output, making it a favorite among classic car enthusiasts and restorers.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,499 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.0 mm × 60.0 mm | |
| Power output | 63 kW (86 PS) @ 6,000 rpm | |
| Torque | 125 Nm @ 4,500 rpm | |
| Fuel system | Carburetor (Solex 32-32 DIDTA or Pierburg 2E3) | |
| Emissions standard | Euro 1 (pre-1980); Early Euro 2 (1980–1984) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Single-row timing chain | |
| Oil type | SAE 10W-40 mineral oil | |
| Dry weight | 138 kg |
The carbureted SOHC design provides smooth, linear power delivery ideal for classic driving but requires regular carburetor tuning and choke adjustment for cold starts. SAE 10W-40 mineral oil is recommended for optimal timing chain lubrication and bearing protection. The single-row timing chain is robust but should be inspected every 80,000 km for stretch. The engine's mechanical simplicity makes it highly serviceable and durable when maintained properly. Fuel economy is modest by modern standards, but the engine is tolerant of lower-octane fuels due to its low compression ratio. Periodic valve clearance checks (every 20,000 km) are essential to maintain performance and prevent valvetrain noise.
Oil Specs: Specifies SAE 10W-40 mineral oil (BMW Service Bulletin 11 00 75). Synthetic oils not recommended due to seal compatibility.
Emissions: Pre-1980 units meet Euro 1; 1980+ models meet early Euro 2 (VCA Type Approval #VCA/EMS/1029). No catalytic converter on early models.
Power Ratings: Measured under DIN 70020 standards. Output consistent across production runs (BMW TIS Doc. A10050).
BMW Technical Information System (TIS): Docs A10050, A10150, A10200
BMW Group Historical Archive
VCA Type Approval Database (VCA/EMS/1029)
The BMW M10 B15 was used across BMW's E21 platform with longitudinal mounting. This engine was the base powerplant for the first-generation 3 Series, positioned below the M10 B18 and B20 variants. It received minor tuning adjustments for coupe vs. sedan applications and was phased out in 1984 with the introduction of the M40 engine family. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the front-facing side of the cylinder block, just below the exhaust manifold (BMW TIS A10250). The M10 B15 can be visually identified by its carburetor (Solex or Pierburg), lack of fuel injection, and distributor-mounted ignition system. Critical differentiation from M10 B18: B15 has a shorter stroke (60.0 mm vs. 66.0 mm) and lower power output. Service parts are generally interchangeable with other M10 variants except for pistons, crankshaft, and carburetor tuning (BMW TIS A10050).
The M10 B15 is one of BMW's most reliable classic engines, with minimal inherent design flaws. Internal BMW quality reports from 1985 indicate very low failure rates across its production run. However, age-related degradation and improper restoration practices are common in surviving examples. Regular maintenance, correct fluid specification, and proper storage are critical for preserving engine integrity beyond 150,000 km.
Analysis derived from BMW technical bulletins (1975–1984) and historical failure data. Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW M10B15.
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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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Vehicle Certification Agency (VCA)
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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