Enhance Your BMW S55 with Mosselman 85c Oil Thermostat Upgrade

by Dan May 5, 2026

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

The BMW S55 engine found in the M2 Competition, M3, and M4 is celebrated for its power, response, and tuning potential. However, it is equally known for running hot—especially when driven hard or modified. High oil temperatures can limit performance and reduce long-term reliability, making effective oil cooling essential for enthusiasts. The Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver is engineered to solve these issues by lowering and stabilizing oil temperatures, ensuring your BMW delivers consistent performance in all driving conditions.

What the Mosselman S55 Oil Thermostat Does

Factory oil thermostats on the N54, N55, and S55 engines typically allow oil temperatures to climb to around 120°C during normal driving. While this is considered acceptable by OEM standards, it can lead to heat soak, performance inconsistency, and added stress on engine components—particularly in tuned or aggressively driven vehicles.

The Mosselman S55 Oil Thermostat 85c opens at a significantly lower 85°C, effectively reducing the operating temperature by approximately 20°C. This results in a more stable oil temperature, typically between 95°C and 105°C depending on the model. By keeping the oil cooler, your engine is exposed to less thermal stress and can deliver power more consistently.

Why a Lower Oil Temperature Matters

High-performance turbocharged engines rely heavily on oil for both lubrication and cooling. When oil temperatures rise too high, viscosity drops and protective properties weaken. Over time, this can lead to premature wear, reduced turbocharger longevity, and increased risk of engine damage under load.

By installing the Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver, drivers benefit from improved thermal management, helping protect vital engine components and maintain peak performance—especially important for vehicles with ECU tuning, upgraded turbos, or frequent track use.

Key Benefits of the Mosselman 85c Thermostat

20°C lower operating temperature compared to the stock thermostat.
More stable oil temperatures for improved reliability and power consistency.
Equipped with a true thermostat mechanism—not an always-open design—making it suitable for both hot and cold climates.
Maintains normal warm-up times, avoiding excessive cold-start wear.
Made from a solid block of high-grade aluminum for strength and durability.
Fast installation—typically around 30 minutes.

A High-Quality, Plug-and-Play Performance Upgrade

The Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver is manufactured from high-grade aluminum, precision-machined from a solid block for superior durability. Unlike many lower-cost alternatives, this unit features a real thermostat element, ensuring optimal performance in all environmental conditions rather than relying on an always-open design that can lead to slow warm-up times.

Installation is completely plug-and-play. While the thermostat itself is included, Mosselman strongly recommends pairing it with the MSL Installation Kit and the MSL Titanium GR5 Hex-Race Bolt Set to ensure a leak-free and secure fit. An oil change is required during installation, making it an ideal upgrade when servicing your vehicle.

Perfect for Tuned and Hard-Driven BMWs

Cars running higher boost levels, performance software, or upgraded turbos naturally generate more heat. The Mosselman thermostat helps mitigate these heat-related issues by preventing temperatures from climbing into danger zones during spirited driving, track days, or even summer commutes.

For daily drivers, this thermostat provides peace of mind by improving long‑term engine health. For track enthusiasts, it helps maintain consistent lap-to-lap performance by reducing thermal heat soak. For tuned vehicles, it helps safeguard your investment and protect against oil overheating—a common issue in higher-output S55 builds.

Compatibility

This thermostat fits a wide range of BMW models equipped with the S55 engine, including:

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

It also fits other N55 platforms including the BMW F30 330e/ActiveHybrid 3.

Recommended Supporting Components

To ensure perfect installation and long-term reliability, Mosselman recommends adding the following:

MSL Oil Thermostat Installation Kit – includes required O-rings and oil filter housing gasket.
MSL Titanium GR5 Hex-Race Bolt Set – high-strength, lightweight, corrosion-resistant fasteners.

These components help prevent leaks and provide a secure, long-lasting fit.

Why Choose the Mosselman S55 Oil Thermostat?

Mosselman has a long-standing reputation in BMW performance engineering. Their products are designed, tested, and manufactured to rigorous standards, making them a trusted choice for enthusiasts worldwide. The Mosselman S55 Oil Thermostat 85c (Inc. M2 Competition, M3 & M4) - Silver stands out for its precision, reliability, and proven benefits for engine longevity and performance stability.

Final Thoughts

If you’re looking to improve the reliability and performance consistency of your S55-powered BMW, the Mosselman S55 Oil Thermostat 85c is one of the most essential upgrades available. Whether your car is stock, lightly modified, or heavily tuned, keeping oil temperatures under control is crucial for protecting your engine and maintaining optimal performance. With its high-quality construction, plug‑and‑play installation, and proven cooling advantages, this thermostat offers exceptional value for any BMW enthusiast.

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