BMW N55 85C Low Temp Oil Thermostat | Mosselman OTN55.T85 Cooling Upgrade for F-Series M135i M235i 335i 435i M2 F87 (F20 F21 F22 F30 F31 F32 F33 F34 F36) Oil Cooler Stat / Performance Thermostat Direct Fit

Keep N55 oil temperatures under control with the Mosselman 85°C thermostatic upgrade

Beat heat soak, stabilise oil viscosity and protect your turbocharged straight-six with this 85°C thermostatic oil control unit from Mosselman. On standard hardware, oil temperature on these F series six-cylinder petrol models can creep towards 120°C during enthusiastic driving. This unit begins regulating much earlier at 85°C, typically resulting in an operating window of around 95 to 105°C depending on vehicle, conditions and usage. The result is repeatable performance and improved long-term engine health for fast road and track-day use.

Unlike crude always-open solutions, this is a genuine thermostat that allows proper warm-up in cold weather while delivering stronger temperature management once hot. The high-grade billet aluminium housing is robust, a straight replacement for the factory assembly, and fits cleanly without modification.

Why enthusiasts choose this 85°C stat

• Earlier opening temperature for quicker oil cooling under load
• Typically around 20°C lower peak oil temps than stock, aiding bearing and turbo longevity
• Real thermostat function maintains correct warm-up for year-round drivability
• Billet aluminium body for strength and durability
• Direct-fit replacement - plug-in solution with no coding required
• Approx. 30 minutes install time for experienced technicians

Real-world benefits

• Consistent power delivery on spirited drives and track sessions
• More stable oil pressure and viscosity for reliability
• Highly recommended when tuned or remapped

Compatibility

Designed for BMW F series models with the N55 engine:

• 1 Series M135i - F20 F21
• 2 Series M235i - F22
• M2 - F87
• 3 Series 335i - F30 F31
• 3 Series GT 335i - F34
• 4 Series 435i - F32 F33
• 4 Series Gran Coupe 435i - F36

Note: For E series 135i and 335i with the N55 engine, use the N54-spec oil thermostat.

Recommended extras

• MSL Installation Kit - helps prevent leaks during refit. Includes 2 x oil hose O-rings and 1 x rubber oil filter housing gasket.
• MSL Titanium GR5 Hex-Race Bolt Set

Fitting and service advice

• We strongly advise replacing engine oil and the filter when installing the thermostat.
• Professional installation available at MJ Modifications, Warwickshire. Request a quote: info@mjmodifications.co.uk

Fitment check before dispatch

We can verify compatibility for you. Provide your UK registration number or the last 7 digits of your VIN at checkout and we will confirm before shipping.

Part number

OTN55.T85

Manufacturer

Mosselman

Trusted by us and our customers: We run this unit on our own N55-powered cars and it remains a customer favourite for dependable oil temperature control on street and track.

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