The BMW M10 B18 is a 1,766 cc, inline-four petrol engine produced from 1975 to 1988 as part of BMW's long-running M10 series. It features a cast-iron block, aluminium head, SOHC valvetrain with two valves per cylinder, and Bosch L-Jetronic fuel injection in later variants. In standard form it produced 77 kW (105 PS), offering balanced performance and reliability for compact executive sedans and coupes.
Fitted primarily to the E21 3 Series and early E30 models, including the 316 and 318 variants, the M10 B18 was engineered for smooth responsiveness and mechanical durability. Its emissions compliance was achieved through thermal reactor exhaust manifolds or early catalytic converters on post-1979 models, meeting U.S. and European standards of the era without requiring unleaded fuel in initial versions.
One documented evolution is the transition from carburetted to fuel-injected variants, with the B18 designation indicating the 1.8L displacement. In 1979, BMW introduced the L-Jetronic system on North American and high-emissions-market models to meet tightening regulations. This change improved idle stability and fuel metering accuracy, forming the basis for later M40 engine management systems.
Pre-1979 models meet U.S. EPA 1975 standards; 1979–1988 variants comply with Euro 1 (VCA UK Type Approval #VCA/EMS/1122).
The BMW M10 B18 is a 1,766 cc inline-four petrol engine developed for compact BMW platforms (1975–1988). It combines a robust SOHC valvetrain with Bosch L-Jetronic electronic fuel injection (on later models) to deliver linear power delivery and strong mid-range response. Designed during a period of increasing emissions regulation, it balances mechanical simplicity with evolving environmental requirements.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,766 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 89.0 mm × 71.0 mm | |
| Power output | 77 kW (105 PS) @ 5,800 rpm | |
| Torque | 150 Nm @ 4,200 rpm | |
| Fuel system | Bosch L-Jetronic (EFI) or Solex 32-32 DIDTA carburettor | |
| Emissions standard | Pre-cat (1975–1978), Euro 1 (1979–1988) | |
| Compression ratio | 9.0:1 (carb), 9.5:1 (EFI) | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (single-row, durable design) | |
| Oil type | SAE 10W-40 mineral or semi-synthetic | |
| Dry weight | 137 kg |
The SOHC design provides predictable performance and low maintenance demands, but requires adherence to 15,000 km valve clearance checks and timing chain inspections. Use of leaded or low-octane fuel can damage early non-catalyst exhaust systems; post-1979 models require unleaded petrol to protect catalytic converters. The L-Jetronic system demands clean fuel and functional sensors to prevent drivability issues. Classic car owners should verify cooling system integrity and replace rubber hoses periodically to prevent overheating. The M10's over-square bore/stroke ratio enhances high-RPM breathing, making it suitable for spirited driving within mechanical limits.
Oil Specs: Requires SAE 10W-40 (BMW Service Bulletin 11 01 79). Modern synthetic oils compatible if viscosity matches.
Emissions: Euro 1 certification applies to 1979–1988 production only (VCA Type Approval #VCA/EMS/1122). Pre-1979 models meet U.S. EPA 1975 standards.
Power Ratings: Measured under DIN 70020 standards. Output varies slightly between carburetted and fuel-injected models (BMW TIS Doc. A18210).
BMW Technical Information System (TIS): Docs A18200, A18201, A18202, A18210
VCA Type Approval Database (VCA/EMS/1122)
DIN 70020 Engine Power Measurement Standard
The BMW M10 B18 was used across BMW's E21 and E30 platforms with longitudinal mounting and no external licensing. This engine received model-specific tuning variations-carburetted versions for European base models and L-Jetronic fuel injection for North American and higher-trim vehicles-and from 1982 the E30 platform introduced revised intake manifolds and distributor configurations, creating minor service distinctions. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the front-facing side of the cylinder block near the exhaust manifold (BMW TIS A18202). The 7th VIN digit indicates engine family ('M' for M-series). Carburetted models have a chrome air cleaner cover and twin-choke Solex unit; fuel-injected variants feature a black plastic intake plenum and Bosch ECU under the hood. Critical differentiation from M10 B16: B18 has a longer stroke (71.0 mm vs. 66.8 mm) and larger displacement. Service parts require model-year verification - L-Jetronic components (injectors, ECU, sensors) are not interchangeable with carburetted systems.
The M10 B18's primary reliability risk is cooling system failure due to age-related degradation, with elevated incidence in vehicles stored outdoors or used infrequently. Internal BMW field reports from 1985–1990 noted a moderate number of head gasket failures on high-mileage examples, while UK DVLA records show electrical faults as a leading cause of MOT failures in classic E21/E30 models. Poor maintenance and use of incorrect coolants increase system stress, making coolant replacement and hose inspection critical for long-term ownership.
Analysis derived from BMW technical bulletins (1975-1988) and UK DVLA failure statistics (1985-1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW M10B18.
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