BMW M30B25 engine

M30 series power units are considered to be the most successful engines of the German automaker. BMW cars were equipped with these motors for almost a quarter of a century (1968-92)! They were popular due to a long service life, unpretentiousness in maintenance, lack of major problems. 26 years have passed since the moment of release of the last unit, but still different cars use this motor. Here we will do a review of the smallest unit, the M30B25.

Let’s consider technical characteristics of the unit M30B25, which was produced for 7 years (1968-75) and installed on BMW cars with bodies E12/23/28:

The cylinder block is made of cast iron. Many people ask what kind of gasoline uses M30B25 and what oil to pour into its gearbox? It is AI-92. Fuel consumption per 100 km in the mixed cycle is 9.8 liters. Motor oil is used with viscosity 5W-30/40 and 10/15W-40. There should be 5.75 liters of oil in the engine, replacement is recommended after 7-10 thousand km.

M30B25 engine specifications

Advantages

The engine has a long service life. A car with such a motor can drive 500 thousand kilometers, and in some cases, the mileage will be more. The engine design and its problems are well studied. Therefore, repair/replacement of faulty units is carried out quickly. However, with each year it is increasingly difficult to find components. After all, the motor has long been out of production.

The timing mechanism uses a chain, which also contributes to a long service life. The power supply system before 1979 is carburetor, after 1979 – injector (they are more widespread).

Disadvantages

We said above that this motor is ultra-reliable. However, even with such engines, there are drawbacks. According to car owners’ reviews, the power unit is inherent in the following problems:

• Overheating. In 9 cases out of 10, the cause is the cooling system. This defect is inherent in almost all engines of the concern. Check radiator for contamination, thermostat and pump. If the antifreeze has been replaced, air plugs may be present;
• Cracks. The second major problem with BMW installations. They appear in the cylinder block. Typically in the area of the bolt threads. Symptoms are Increased consumption of antifreeze and/or the formation of emulsion in the engine oil. Basically, this problem is solved by replacing the faulty assembly. Repairs are rarely performed;
• M30B25 has no spark. It is likely that the DPKV has failed or is dirty. You can blow it out with a compressor and/or flush it with solvent. If there is no spark again, you will need a replacement.

The M30B25 requires quality oil (this applies to all BMW engines) and it is not adapted for prolonged driving in a sporty style, because it is not a sport engine. However, it should be noted that all the deficiencies mentioned above begin to appear after prolonged use of the power unit and without proper preventive maintenance of the engine components.

Chip tuning

Tuning allows you to get a turbo engine M30B25. You need to buy a Chinese turbo kit designed for BMW M30. You mount its engine stock and inflate it to 1 bar. As a result, you can get a power of 400 “horses”! However, turbines made in the PRC can be operated for a few thousand kilometers, and then you have to change them. For long-term operation, it is recommended to take the original Garrett GT35, but its cost is much higher.

With chip tuning you can turn an M30B25 setup into an M30B30, with 89mm bore. you need to replace the pistons, crankshaft and bore the block from 86 to 89mm.

Whether it’s worth tuning or not is up to you. It’s just that the M30B25 engine is old. We would recommend getting the M50 setup. After all, it is more recent.

This engine is installed on the following models:

BMW 5-Series (E28)

BMW 5-Series (E12)