Oil Cooler Thermostats

When should the engine oil actually start flowing through the oil cooler? That is decided by the thermostat. In this category you will find oil cooler thermostats for you who want to control oil temperature precisely in a project with an aftermarket oil cooler.

What does an oil cooler thermostat do?

The thermostat typically keeps the oil bypassing the cooler while the engine is cold, so it reaches operating temperature faster. At a certain temperature it opens and directs the oil through the cooler. A low opening temperature, e.g. the HKS thermostat at 75 degrees, can send the oil to the cooler earlier during hard driving. The thermostat is typically used in oil cooler kits or together with a separate engine oil cooler.

How to choose a thermostat

• Opening temperature: a low value can give cooler oil on track days, but the oil can get too cold on short trips in cold weather.
• Compatibility: the thermostat must fit your specific oil cooler system or filter adapter – check the part number.
• Use: daily driving and track driving place different demands on oil temperature.

Installation and maintenance

Keep an eye on the oil temperature after installation. If the thermostat sticks in the closed position, the oil can overheat; if it sticks open, the oil can struggle to reach operating temperature. See also other oil and fluid coolers and our other HKS parts.

Frequently asked questions

What does 75 degrees mean on an oil cooler thermostat?

It is the temperature at which the thermostat typically starts to open and send oil through the cooler. A lower opening temperature means the cooler comes into use earlier than with a thermostat that opens at a higher temperature.

Can I run without a thermostat in the oil cooler system?

It is possible in some systems, but then the oil always flows through the cooler. This can mean the engine takes longer to reach operating temperature, especially in cold weather and on short trips.

How do I know if the thermostat is faulty?

If the oil temperature rises significantly under load, the thermostat may be stuck closed. If the oil rarely reaches normal temperature, it may be stuck open. Other faults in the system can cause the same symptoms, so check the entire system.