Upgrade BMW Cooling with Mosselman S55 Oil Thermostat 85c - M2/M3/M4

by Dan May 4, 2026

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Upgrade Your BMW’s Cooling System with the Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver

BMW’s turbocharged performance engines, especially the S55, N54, and N55, are well known for their impressive power potential. Unfortunately, they are also known for running hot—sometimes too hot. Elevated oil temperatures can lead to reduced engine performance, heat soak, and long-term reliability issues. That’s where the Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver comes in. This precision-engineered upgrade is designed to address the oil cooling limitations in some of BMW’s most popular performance models.

What Is the Mosselman S55 Oil Thermostat?

The Mosselman S55 Oil Thermostat 85c is a plug-and-play replacement for the factory thermostat found in BMW S55, N54, and N55 engines. Unlike the stock unit—which typically allows oil temps to climb to around 120°C during normal driving—the Mosselman thermostat opens at a lower 85°C threshold. This results in more stable and significantly cooler operating temperatures, usually between 95°C and 105°C depending on the model.

Constructed from a solid block of high-grade aluminum, this thermostat is built for strength, reliability, and durability. Most importantly, it uses a real thermostat mechanism rather than an always-open setup, ensuring proper oil warm-up even in colder climates.

Why Oil Temperature Control Matters

Oil temperature isn’t just a number—it affects nearly every aspect of engine performance and longevity. When oil temperatures rise too high, oil viscosity drops, reducing the lubrication your engine needs for safe operation. This can increase engine wear, decrease performance, and shorten the life of critical components.

BMW’s factory cooling system tends to run hot, especially in tuned or aggressively driven cars. Upgrading to the Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver helps maintain more consistent oil temperatures, protecting your engine under both daily driving and high-performance conditions.

Key Benefits of the Mosselman S55 Oil Thermostat

20°C Lower Operating Temperatures – Helps keep oil temps in the optimal range for performance and engine protection.
Real Thermostat Operation – Suitable for all climates, unlike always-open designs that can cause underheating in cold weather.
Improved Engine Reliability – Cooler, stable oil temperatures reduce wear and stress on internal engine components.
Performance Stability – Reduces heat soak and maintains power during spirited driving, track days, or tuned applications.
High-Quality Construction – Milled from a solid block of high-grade aluminum for long-lasting durability.
Fast Installation – Can be installed in about 30 minutes.

Who Should Install This Oil Thermostat?

The Mosselman S55 Oil Thermostat 85c is beneficial for a wide range of BMW owners, but it is especially useful for:

Owners of tuned S55, N54, or N55 engines
Drivers who frequently enjoy spirited or track driving
Anyone experiencing high oil temperatures or heat soak
BMW M2 Competition, M3, and M4 drivers looking for performance reliability upgrades
Owners who want better long-term engine protection

If you own a BMW with the S55 engine, this upgrade is almost essential. Even stock vehicles can see increased reliability from maintaining cooler oil temperatures.

Real-World Use Cases and Advantages

Whether you daily-drive your BMW or take it to the track, cooler and more controlled oil temperatures offer significant advantages:

Smoother and more reliable power during aggressive acceleration
Reduced risk of overheating on hot days
Less thermal stress on turbos and internal engine components
Better consistency during prolonged track sessions
Enhanced drivability for tuned cars producing higher boost levels

For hybrid owners, such as those with the BMW F30 330e or ActiveHybrid 3 using the N55 engine, the Mosselman S55 Oil Thermostat 85c also provides improved thermal stability under demanding conditions.

What’s Included and What You’ll Need

The thermostat package includes the oil thermostat itself. However, gaskets and bolts are not included. To ensure a complete and leak-free installation, Mosselman highly recommends pairing the thermostat with the MSL Installation Kit and the MSL Titanium GR5 Hex-Race Bolt Set.

The installation kit contains essential O-rings and a rubber oil filter housing gasket. Because removing the thermostat requires draining the oil, an oil change is also needed during installation.

Compatibility

The Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver is compatible with a wide range of BMW performance models using the S55 engine, including:

BMW M2 Competition F87
BMW M3 F80, including Competition and CS
BMW M4 F82/F83, including Competition, CS, and GTS

It also fits other BMW models equipped with the N55 engine, such as the BMW F30 330e/ActiveHybrid 3.

Many retailers offer a compatibility check using your vehicle’s registration or VIN to ensure proper fitment before purchasing.

Why Choose Mosselman?

Mosselman is known for producing premium, race-proven performance parts engineered in-house with exceptional quality standards. Their components are trusted by enthusiasts, tuners, and professional drivers for their precision, reliability, and performance gains.

Conclusion

The Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver is one of the smartest upgrades you can make to protect and enhance your BMW’s engine. By reducing oil temperatures and improving thermal stability, it delivers better performance, increased reliability, and peace of mind under all driving conditions.

If you want your BMW to run cooler, perform more consistently, and last longer—this thermostat is a must-have addition to your build.

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