The BMW M30B30 (306EA) is a 2,986 cc inline-six petrol engine, part of the legendary M30 engine family introduced in 1968. It features a single overhead camshaft (SOHC) design with a chain-driven valvetrain, Bosch L-Jetronic fuel injection, and a compression ratio of 9.0:1. Producing 185–218 bhp (138–163 kW) at 5,800–6,500 rpm and 270–290 Nm of torque at 4,000 rpm, it was engineered for smooth operation, refined power delivery, and durability in BMW’s flagship sedans and coupes.
Fitted to the E24 6 Series (630CS/635CSi), E28 5 Series (530i/535i), and E32 7 Series (730i/735i) from 1976 to 1991, the M30B30 (306EA) served as BMW’s high-performance inline-six during a period of increasing electronic engine management. It was designed for relaxed cruising and long-distance comfort, with a cast-iron block and aluminum head. The engine met early European emissions standards (pre-Euro 1) and was tuned for linear power delivery and responsive throttle response.
While mechanically robust, the M30B30 (306EA) is susceptible to age-related wear in the timing chain, valve seals, and fuel injection components. No major factory service bulletins were issued specifically for the B30 variant, but general M30-series maintenance guidance (BMW Service Information 11 03 01) emphasizes inspection of the timing chain tensioner every 60,000 km to prevent valve damage. Later M30 engines (e.g., M30B35) offered larger displacement, but the B30 remains a sought-after unit for E24 and E28 restorations.
The M30B30 (306EA) predates formal Euro emissions standards, complying with German TÜV and EU type-approval regulations applicable to vehicles produced between 1976 and 1991 (EU Directive 70/220/EEC, amended).
The BMW M30B30 (306EA) is a 2,986 cc SOHC inline-six petrol engine produced from 1976 to 1991, primarily for the E24, E28, and E32 platforms. It features Bosch L-Jetronic or Motronic fuel injection and a chain-driven camshaft, delivering smooth power with proven mechanical durability. Designed before modern emissions regulations, it represents the peak evolution of BMW’s naturally aspirated M30 engines.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,986 cc | |
| Fuel type | Petrol (Unleaded RON 95) | |
| Configuration | Inline-6, SOHC, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 86.0 mm × 86.0 mm | |
| Power output | 185–218 bhp (138–163 kW) @ 5,800–6,500 rpm | |
| Torque | 270–290 Nm @ 4,000 rpm | |
| Fuel system | Bosch L-Jetronic or Motronic fuel injection | |
| Emissions standard | Pre-regulatory (EU Directive 70/220/EEC) | |
| Compression ratio | 9.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Single-row timing chain | |
| Oil type | SAE 10W-40 mineral or semi-synthetic | |
| Dry weight | 190 kg |
The M30B30 (306EA) is a durable, low-maintenance engine ideal for classic car enthusiasts and restorers. It requires regular timing chain tensioner inspection (every 60,000 km) to prevent valve damage, as it is an interference engine. Fuel injection maintenance—cleaning injectors, replacing the fuel filter, and checking vacuum lines—is essential for smooth operation. Use of unleaded fuel requires inspection of valve seat condition; hardened inserts may be necessary. The SOHC design allows operation on modern RON 95 petrol. Oil changes every 10,000 km with SAE 10W-40 ensure longevity of the hydraulic lifters and camshaft.
Oil Specs: No BMW Longlife specification existed; mineral or semi-synthetic 10W-40 meeting API SF/CD standards is recommended (BMW Service Manual E28).
Emissions: Pre-dates Euro standards; compliant with EU Directive 70/220/EEC as implemented in Germany (TÜV D-76-030).
Power Ratings: Measured under DIN 70020 standards. Output varies slightly based on ignition timing and fuel pressure (BMW Group Service Manual E32).
BMW Technical Information System (TIS): Docs M30-001, M30-003, M30-004, SIB 11 03 01
BMW ETK Parts Catalogue (1976–1991)
German TÜV Type Approval Database (D-76-030)
ISO 1585: Road vehicles — Engine test code — Net power
The BMW M30B30 (306EA) was used across BMW's E24, E28, and E32 platforms with longitudinal mounting and rear-wheel drive. This engine received platform-specific adaptations—L-Jetronic (pre-1987) and Motronic (post-1987)—and from 1987 the E32 735i facelift, 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 M30-005). The full engine code begins with "M30B30" followed by a serial number. The VIN prefix (E24, E28, or E32) confirms chassis compatibility. Visual cues include a black valve cover with "Bosch L-Jetronic" or "Motronic" label, a single throttle body, and a distributor mounted at the rear of the engine. Critical differentiation from M30B25: The B30 has a 2,986 cc displacement (86.0 mm bore, 86.0 mm stroke) versus 2,494 cc (84.0 mm bore, 71.0 mm stroke) for the B25. Crankshaft, connecting rods, and intake manifold also differ.
The M30B30 (306EA)'s primary reliability risk is timing chain wear due to age or neglect, which can result in bent valves due to its interference design. While the engine block and crankshaft are highly durable, fuel injection wear, valve seal leakage, and distributor cap corrosion are common in high-mileage or poorly maintained examples. UK DVLA MOT failure data from 2020–2023 indicates that 32% of E28 535i models fail due to emissions or idle instability, often linked to fuel injection issues. Adherence to maintenance schedules and use of quality replacement parts are critical for long-term operation.
Analysis derived from BMW technical bulletins (1976–1991), ETK parts documentation, and UK DVLA MOT failure statistics (2020–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW M30B30-306EA.
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