Compact High-Flow Engine & Transmission Oil Cooler Thermostat, 205°F

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SKU: FSC-205
Regular price $159.00

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Improved Racing's Flow Series Compact (FSC) oil thermostat is an ultra-compact unit designed for use in cooling systems for transmissions, differentials, transaxles and small engines where flow rates do not exceed 5 GPM. This thermostat is perfect for engine oil cooling in motorcycles, ATVs, go karts, and other small engines.

The device's unique, patented internal design (US patent 9,772,632) ensures a low pressure drop by placing the bypass valve mechanism completely out of the primary oil flow. This arrangement also allows for a compact design.

Without a thermostat, oil and transmission fluid coolers are likely to over-cool the fluid, delaying engine warm-up and resulting in horsepower loss, excessive engine wear and reduced gas mileage. Oil thermostats perform the critical function of bypassing the cooler until the oil has reached its minimum operating temperature.

The thermostat maintains the oil exiting the engine at the rated minimum temperature in most conditions. It features female -6AN O-ring boss threads and is available with optional hose barb and male AN adapter fittings. The included brackets allow for multiple mounting options.


Features and Benefits

  • Reduces excessive engine wear and horsepower losses while improving gas mileage by preventing oil temperatures from dropping below optimal levels
  • Patented, high flow, low pressure drop design locates the valve assembly completely out of the primary fluid flow
  • Maintains a minimum fluid temperature according to the typical stabilization temp in the table below, +/- 2°F (+/- 1°C)
  • Allows a small percentage (less than 10%) of fluid to continually circulate through the cooler to eliminate air pockets and prevent cold fluid trapped in the cooler from shocking the system
  • Rebuildable
  • 6061-T6 billet aluminum construction with black MIL-A-8625 Type II anodized finish
  • Lightweight at just 7.5 ounces (212g) without brackets or fittings

Temperature Rating Specifications

Part Number Typ. Stabilization Temp Activation Temp Full Flow Temp
FSC-145 145ºF (63ºC) 140ºF (60ºC) 163ºF (73ºC)
FSC-165 165ºF (74ºC) 160ºF (71ºC) 181ºF (83ºC)
FSC-185 185ºF (85ºC) 180ºF (82ºC) 203ºF (95ºC)
FSM-205 205ºF (96ºC) 200ºF (93ºC) 221ºF (105ºC)
FSC-215 215ºF (102ºC) 212ºF (100ºC) 233ºF (112ºC)


Valve assembly is completely housed between the two ports.

No valves, springs, or thermal motor interrupting the primary oil flow!

Ultra-compact dimensions (shown in inches)


Brackets allow for multiple mounting configurations

Available with optional hose barb and male AN adapter fittings


  • Fluid cooling systems flowing up to a maximum of 5 GPM (18.93 LPM).
  • Fluid cooling systems for automotive and small vehicle transmissions, transaxles, transfer cases and differentials.
  • Oil cooling systems for small engines such as motorcycles, ATVs, go karts, snowmobiles, and small marine engines.
  • Not for use with corrosive fluids. If used with water, a distilled water solution with a lubricant such as ethylene glycol must be used.


  • 1x Compact remote thermostat block
  • 2x Zinc-plated steel mounting brackets and screws


Part #
FSC Configurator
Improved Racing
Part Weight
1.00 lb (0.45 kg)
Primary Material
6061-T6 aluminum
Type II Anodized
Minimum Operating Temperature
-40°F (-40°C)
Maximum Operating Temperature
302°F (150°C)
Inlet Port Size
-6AN O-Ring Boss Female
Outlet Port Size
-6AN O-Ring Boss Female
Maximum Operating Pressure
300 psi (20.68 bar)
Max Recommended Flow Rate
Up to 5 GPM (19 LPM)
Fluid Compatibility
Engine oil
Power Steering Fluid
Transmission fluid


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