Upgrade Your BMW M: Mosselman S55 Oil Thermostat for Cool Performance

by Dan May 17, 2026

Why the Mosselman S55 Oil Thermostat 85c Is a Must‑Have Upgrade for BMW M2 Competition, M3, and M4 Owners

The Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver is one of the most effective reliability upgrades available for BMW S55-powered models. Whether you own a BMW M2 Competition, M3, M4, or even certain N55-powered models such as the F30 330e, maintaining safe and stable oil temperatures is essential for consistent performance and long-term engine health. This upgraded oil thermostat is engineered specifically to tackle the oil cooling limitations that many BMW engines are known for.

What Is the Mosselman S55 Oil Thermostat 85c?

The Mosselman S55 Oil Thermostat 85c is a precision-engineered, plug-and-play replacement for the factory oil thermostat found in BMW S55 and compatible N55 engines. BMW’s stock thermostat typically allows oil temperatures to climb to around 120°C under normal driving conditions. High oil temperatures not only reduce performance, but also increase wear and stress on engine components, especially on tuned or aggressively driven vehicles.

The Mosselman unit solves this problem by opening at a much lower 85°C. This keeps oil temperatures in a safer and more stable range—typically between 95°C and 105°C depending on the specific model. By actively controlling and lowering the operating temperature, the thermostat improves both reliability and performance consistency.

Why BMW S55 and N55 Engines Benefit From Cooler Oil Temperatures

The S55 and N55 engines are renowned for performance, but they are equally known for oil temperature challenges. High oil temperatures can lead to issues such as:

Heat soak during spirited driving
Inconsistent performance as temperatures rise
Reduced lubrication efficiency
Premature engine wear
Increased risk for tuned engines producing more power

The Mosselman S55 Oil Thermostat 85c provides a simple yet highly effective solution by lowering the oil temperature threshold. This ensures the engine operates within a safer thermal zone without compromising warm-up time.

Key Benefits of the Mosselman S55 Oil Thermostat 85c

Drivers upgrade to the Mosselman thermostat for several strong reasons. When installed, owners can expect:

20°C lower operating temperature compared to stock
Greater power consistency during long drives or track sessions
Enhanced long-term engine reliability
Reduced thermal stress on internal components
Faster recovery from heat soak
Improved performance stability for tuned vehicles

Unlike some aftermarket solutions that remain open at all times, the Mosselman design uses a real thermostat. This means your oil still reaches optimal operating temperature quickly, making it suitable for both hot and cold climates.

High-Quality Construction and Fast Installation

The Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver is crafted from a solid block of high-grade aluminum. This ensures long-term durability and resistance to heat cycling—an important consideration for high-performance BMW engines. The robust construction prevents deformation and leaking under pressure, offering years of dependable service.

Installation typically takes around 30 minutes, making it one of the most straightforward reliability upgrades for BMW S55 engines. Because changing the thermostat requires draining the oil, an oil change should be performed at the same time.

Mosselman also recommends pairing the thermostat with the MSL Installation Kit and the MSL Titanium GR5 Hex-Race Bolt Set. These accessories prevent leaks and ensure a secure fit by replacing all necessary gaskets and bolts.

Ideal Use Cases for the Mosselman Oil Thermostat

This thermostat is suitable for a wide range of driving styles and performance requirements. It is especially useful for:

Daily driven BMW M2, M3, or M4 models that regularly experience high temperatures
Tuned vehicles running higher boost, fuel upgrades, or performance mapping
Track day or spirited weekend drives where heat management is crucial
Owners looking to improve the long-term reliability of their S55 or compatible N55 engine
Hybrids and special models such as the BMW F30 330e/ActiveHybrid 3

The Mosselman S55 Oil Thermostat 85c helps protect your engine under demanding conditions while still functioning comfortably during normal commuting.

Compatibility

The thermostat is compatible with multiple BMW platforms equipped with the S55 engine, including:

BMW M2 Competition F87 S55
BMW M3 F80 / M3 Competition / M3 CS
BMW M4 F82 / M4 Competition / M4 CS / M4 GTS

It also fits the BMW F30 330e and ActiveHybrid 3 with the N55 engine.

A compatibility check using your VIN or UK registration number is performed prior to dispatch to ensure the correct fitment.

Why This Upgrade Is Worth It

The Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver is more than a performance part—it is a reliability investment. With lower oil temperatures, your engine experiences less stress, allowing you to enjoy the full capability of your BMW without worrying about heat-related issues. For tuned vehicles or drivers who demand consistent performance, this upgrade is practically essential.

Mosselman’s engineering expertise and premium construction materials make this thermostat one of the best options on the market for BMW owners. With quick installation, proven temperature control, and clear long-term benefits, it stands out as a smart upgrade for enthusiasts and everyday drivers alike.

For the best results, pair it with the dedicated installation kit and titanium bolt set to ensure a leak-free and secure fit.

Enhance the performance, durability, and confidence of your S55-powered BMW with this exceptional cooling upgrade.