|Successor||BMW M60 V8|
|Engine(s)||2.5 L (2494 cc/152 in³)|
2.8 L (2788 cc/170 in³)
3.0 L (2986 cc/182 in³)
3.2 L (3210 cc/195 in³)
3.4 L (3430 cc/209 in³)
The BMW M30 is an inline-6 cylinder engine built by BMW and was used in many different models since 1968. It was originally developed in the late 1960s as an extended 2.5 liter version of the robust inline four cylinder BMW M10 first used in the 'Neue Klasse' BMW 1500, with which it shares a number of design features, including a 30-degree cant to the right for a lower profile, a crossflow head design, and a chain-driven single overhead cam with rocker arm valve actuation. The 'Big Six,' also known as the 'Senior Six,' got its informal names after the introduction of a smaller BMW M20 belt-driven SOHC six cylinder in the late '70s.
The M30 powered a series of BMW 6-cylinder E9 and BMW E24 coupes to European Touring Car Championship (ETCC) throughout the '70s and into the middle 1980s, even though a more powerful DOHC 24-valve head had been developed for high performance motorsports and street use.
A production turbo variant of the M30 designated the M102B32 or M106B34 (depending on 3.2 or 3.4 liter displacement) was used in the BMW E23 Seven Series where it was designated "745i", based on a then-current projection that the horsepower produced was roughly equal to that of a 4.5 liter normally-aspirated engine. The 3.5 DOHC M5 and M6 engine was used in the South African 745i from 1984-1986.
BMW's M30 straight six cylinder engines had the longest production run of any BMW engine, dating back to the 1968 E3 sedans and E9 coupes. The last use of the block was the 1994 E32 730i. Displacement ranged from 2.5 to 3.4 liters with a 100 mm bore spacing.
The M30 engine's bottom end is virtually 'bulletproof' and a true workhorse. The M30's timing chain is designed to last the life of the engine and it will, if the timing chain tensioner is maintained. Unfortunately, over time and use, the plastic parts in it can fail but they are easily replaced. The alloy head is prone to warping if the engine is overheated (especially around the somewhat restricted cooling system passages near the middle), but with regular cooling system maintenance, oil changes, and other routine maintenance, the M30 can routinely run well past 250,000 miles.
Known Problems 
These problems may not necessarily apply to all versions of the M30 engine.
- An "oil spray bar" is mounted above the camshaft. This hollow metal tube has perforations on its underside that spray oil over the camshaft and rocker arms, but with time the two banjo bolts that hold the bar in place can loosen. As a result, oil passage through the spray bar will get restricted, and some of the camshaft and rocker arms may not get cooled and/or lubricated properly, leading to fatal wear.
- On some models, the return valve in the oil filter housing fails with time, thus making oil run out after stopping the engine, instead of keeping it in the housing. While not a critical problem, it results in the engine needing up to five seconds to build up proper oil pressure upon engine start. BMW replaced the oil filter housing with a more durable valve around 1991.
- While not a problem by design, the spacing between the valve rocker arms and the valves must be adjusted approximately every 30,000 km (20,000 miles). Failure to adjust might lead to poor running, increased fuel consumption, and engine wear.
- The engine fan is mounted with a viscous coupling that expands when heated. As the engine becomes warm, the coupling gets a better grip on the fan, thus leading to increased rotation of the fan, and more airflow. If this viscous coupling fails, the fan will only rotate relatively slowly (as driven by the engine by a V-belt), and will not provide sufficient cooling, leading to overheating. Overheating can extremely quickly lead to engine failure, such as a destroyed headgasket or a warped or partly melted cylinder head.
|Engine||Displacement||Power: kW (hp:BHP/PS) @ RPM||Torque||Redline||CR||Year|
|M30B25LE||2.5 L (2494 cc/152 in³)||110 kW (147/150) @ 5500||215 N·m (158 ft·lbf) @ 4000||9.6||1981|
|M30B28LE||2.8 L (2788 cc/170 in³)||132 kW (174/177) @ 5800||240 N·m (177 ft·lbf) @ 4000||9.3||1977|
|M30B28||135 kW (181/184) @ 5800||240 N·m (177 ft·lbf) @ 4200||6500||9.3||1979|
|M30B30||3.0 L (2986 cc/182 in³)||135 kW (181 hp) @ 5800||255 N·m (188 ft·lbf) @ 3500||1976|
|140 kW (188 hp) @ 5800||260 N·m (191 ft·lbf) @ 4000||6200||9.0||1986|
|M30B32||3.2 L (3210 cc/195 in³)||145 kW (194 hp) @ 5500||285 N·m (210 ft·lbf) @ 4300||1979|
|M30B32LAE||185 kW (248 hp) @ 5200||380 N·m (280 ft·lbf) @ 2600||1980|
|M30B32LE||145 kW (194 hp) @ 5500||280 N·m (206 ft·lbf) @ 4300||1976|
|M30B34||3.4 L (3430 cc/209 in³)||155 kW (207/211hp) @ 5700||305 N·m (224 ft·lbf) @ 4000||6200||1986|
|M30B34M||136 kW (182/185) @ 5400||290 N·m (213 ft·lbf) @ 4000||8.0||1984|
|160 kW (214/218) @ 5500||310 N·m (228 ft·lbf) @ 4000||10.0||1982|
|M30B34MAE||185 kW (248 hp) @ 4900||380 N·m (280 ft·lbf) @ 2200||1982|
|M30B35||155 kW (211PS) @ 5700||305 N·m (225 ft·lbf) @ 4000||6200||9.0||1988|
- 1973-1976 E12 525
- 1976-1981 E12 525
- 1981-1987 E28 525i
2.8 L (2788 cc) Applications:
3.0 L (2986 cc) Applications:
3.2 L (3210 cc) Applications:
- 8.0:1 compression ratio
3.4 L (3430 cc) Applications:
- 1983-1993 Europe
- 1985-1993 US
- 3.4 liter (3430 cc) SOHC inline-6 cylinder
- 9.0:1 compression ratio
- 208 hp @ 5700 rpm
- 225 ft·lbf torque @ 4000 rpm
- 87 AKI / 91 RON octane fuel or better recommended
3.5 L (3453 cc) Applications:
3.5 L (3453 cc) DOHC Applications: