Home 170° Thermostats Application Guide Why A Low Temp Thermostat? 170° vs 180° or 160° 4.6L DOHC Refill/Burp Procedure Where To Buy Contact Us & About Us
170° vs 180° Opening Temperature
Stat 1

These next 4 pics show how our FORD-4D thermostat (right) responds alongside of the 03-04 Mustang Cobra OEM themostat (RT1168) as temps increase while underwater.

Stat 2 This pic shows how the t-stats react to coolant temps in the mid to upper 180s. Even though the stock Cobra thermostat is a 180° unit (left) you can see it actually allows very little flow at these temps. And an OEM GT500 (192°) unit would still be fully closed at this point.
Stat 3 Now it becomes apparent that if you want to keep coolant temps under 190° then you need a thermostat that starts to open around 15-20° lower than that. This is why we believe 170° is the ideal opening temperature for performance applications.
Stat 4 So there's no reason to settle for the poor cold weather performance of a 160° opening temp MORE ON NEGATIVE EFFECTS... Plus Reische Performance thermostats operate more effectively, without the compromise of an improperly fitting bypass, which means our DOHC units will outperform any other low temp thermostat under any condition.
Whether you are using an aftermarket radiator or not, our thermostats will provide the best possible heat dissipation from your setup along with a faster warm up time than a 160° unit or a thermostat with holes drilled in the diaphragm. We believe the 170° opening temp is the ideal balance for high performance engines, providing high flow to your radiator by mid-180 temps while still providing good all season performance. With proper fan settings your coolant temps in cool weather will be in the 170s and in hot weather the 180s, giving those running high levels of timing and/or boost added protection against engine-damaging detonation as well as maximum power output.

Additional Cooling System Improvements

A retune is generally not required with use of our thermostats, however to get the best possible heat dissipation and most consistent temps, your fan settings should be lowered in your tune. Otherwise a low temp thermostat will only be effective when the vehicle is moving because heat cannot be removed unless there is air passing through the radiator. Typically with our 170° thermostat installed your cooling fan(s) should be set to turn on between 184-190° and shut off between 176-182°.

The fan(s) should be able to cycle off in mild ambient outdoor temps with the A/C off, if not then the fan settings are too low. The best way to determine your fan(s) ideal off temp is to warm up the vehicle and drive on a level surface in 70-95° ambient temps at a consistent 50mph. This will establish an engine coolant temp cruise range and your fan(s) should be set to cycle off at, or a degree or two above, your average cruise ECT.

Water transfers heat more effectively than antifreeze so we recommend using the lowest concentration of antifreeze possible for your climate along with a product like Redline Water Wetter. Just make sure you have enough antifreeze in your coolant to keep it from freezing in the winter and always run no less than 20% in a street car. We do not recommend adding Water Wetter to coolant that is more than 40% antifreeze.

More on coolant properties from Redline Oil (PDF Link)

Most people think a larger radiator will improve the capacity of the cooling system but a big factor that is often overlooked is airflow. Increasing airflow will have a dramatic effect on the cooling ability of any radiator which is why most choose to do so when prepping a vehicle for race use. Some common ways to get more air through the radiator are:

  • Increase the size of the lower air dam
  • Box in the radiator to force air to flow through it and not around it
  • Additional hood and fascia vents
  • Additional or more powerful cooling fans

This is also why you never want to remove or obstruct the lower air dam on a modern vehicle. Not to mention it will reduce the life of the radiator fan(s) and could even cause overheating.

Don't hesitate to Contact Us regarding your cooling system issues, we are happy to help!

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