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Blemished - High-Flow Engine Oil Cooler Thermostat

[Part # FSM]

$169.00 $149.00 Free Shipping Details
Fitting Size:
Thermostat Temp:

Please Note: "Blemished" items are parts that exhibit minor aesthetic defects such as scratches, dents, or laser engraving defects that do not affect the functionality of the part. Items may be new or "open box" customer returns. These items come with new hardware and O-ring seals where applicable. "Blemished" items are fully backed by the factory warranty. Photos of a specific item can be provided upon request. Available while supplies last!

This item is blemished for the following reasons:

  • The upper half of the FSM thermostat housings sustained a plating defect, giving them a matte finish instead of the usual gloss finish. The pictures of the built thermostats above show the resulting two-tone appearance. Aside from this aesthetic defect, these thermostats are brand new and in perfect condition.
Improved Racing's Flow Series Motor Sport (FSM) oil thermostat is a universal solution that can be used with any oil cooler on any vehicle or industrial application flowing up to 20 GPM (75.71 LPM).

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.

High performance vehicles require large oil coolers to ensure that the oil does not overheat during strenuous use. These coolers also introduce the danger of over-cooling the oil and delaying engine warm-up, resulting in horsepower loss, excessive engine wear and reduced gas mileage. Oil thermostats perform the critical function of bypassing the oil cooler until the oil has reached its minimum operating temperature.

The thermostat features female -10AN O-ring boss threads and is available with optional fittings in 3/8" or 1/2'' hose barb or AN fittings in -06AN, -08AN, -10AN, or -12AN. The included brackets allow for multiple mounting options.

Supersedes part numbers ENV-100 and EUN-1000.


Features and Benefits
  • Reduces excessive engine or transmission wear and horsepower losses while improving gas mileage by preventing oil temperatures from dropping below optimal levels
  • Maintains a minimum fluid temperature according to the typical stabilization temp in the table below, +/- 2°F (+/- 1°C)
  • Patented, high flow, low pressure drop design locates the valve assembly completely out of the primary fluid flow
  • 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 12.7 ounces (360g) without brackets or fittings
  • Made in the USA and backed by a Lifetime warranty

Temperature Rating Specifications

Part NumberTyp. Stabilization TempActivation TempFull Flow Temp
FSM-145145ºF (63ºC)140ºF (60ºC)163ºF (73ºC)
FSM-165165ºF (74ºC)160ºF (71ºC)181ºF (83ºC)
FSM-185185ºF (85ºC)180ºF (82ºC)203ºF (95ºC)
FSM-205205ºF (96ºC)200ºF (93ºC)221ºF (105ºC)
FSM-215215ºF (102ºC)212ºF (100ºC)233ºF (112ºC)

Unrestricted oil flow through thermostat
Valve assembly is completely housed between the two ports.
No valves, springs, or thermal motor interrupting the primary oil flow!

Compact dimensions
Compact dimensions (shown in inches)

Multiple mounting options
Brackets allow for multiple mounting configurations

Available in -06AN, -08AN, -10AN, -12AN and 3/8 hose barb
Available with 3/8" or 1/2'' hose barb fittings or AN fittings in -06AN, -08AN, -10AN, or -12AN

  • Engine, transmission, differential, and industrial fluid cooling applications flowing up to 20 GPM (75.71 LPM)
  • Passenger car automotive, marine, and experimental aircraft engine oil cooling systems
  • Automotive and truck power steering fluid cooling systems
  • Diesel and gas truck transmission fluid cooling systems
  • Diesel and gas truck differential and transfer case fluid cooling systems
  • 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 Remote thermostat block
  • 4x Black anodized 3/8" or 1/2'' hose barb or -06AN, -08AN, -10AN, or -12AN adapter fittings with Viton O-rings (OPTIONAL)
  • 2x Zinc-plated steel mounting brackets and screws

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