Mishimoto thermostatic sandwich plate fully installed

Mishimoto 2015 Subaru WRX Thermostatic Oil Cooler Kit, Part 3: Testing Results

Interested in purchasing our thermostatic WRX oil cooler? Check out our product page for more information!

Mishimoto Subaru WRX Oil Cooler Kit

It was now time to test our components and ensure that they were operating to our standards. Our previous testing showed that oil warmup was rapid enough for use on a daily driven vehicle. Next we had to confirm that temperature improvements compared to the stock cooler setup were efficient.

We used a similar testing practice with the previous version of this kit, which includes the procedures and conditions listed below.

Testing Conditions

  • Ambient Temperatures: 70°F-75°F
  • Driving Conditions: 6 miles of highway driving at 60 mph
  • Sensors: PLX temperature sensor reading 10 times per second

Setups Tested

  1. Completely stock oil cooler setup
  2. Mishimoto non-thermostatic oil cooler in conjunction with stock oil cooler
  3. Mishimoto thermostatic oil cooler alone

For each test we used our PLX sensors to record fluid temperatures in order to see the comparison of each setups effect on performance.

Check out the results below!

Oil cooler testing results
Oil cooler testing results

So let’s break this chart down into the three separate plots.

Completely stock oil cooler setup

Starting Outlet Temperature: 205°F

Ending Outlet Temperature: 215°F

Peak Temperature: 215°F

The completely stock setup began our testing at just 205°F and quickly rose to 215°F during our 6 minutes of driving. Towards the end of the run the temperature began to taper and steady at 215°F. Keep in mind that this is during normal driving conditions.

Mishimoto non-thermostatic oil cooler in conjunction with stock oil cooler

Starting Outlet Temperature: 178°F

Ending Outlet Temperature: 189°F

Peak Temperature: 191°F

The Mishimoto non-thermostatic kit performed the best out of the three setups. The stock liquid-to-liquid heat exchanger is working with the Mishimoto liquid-to-air cooler to reduce temperatures. It should be noted that towards the end of the run temperatures slightly dropped from the peak. This test showed a drop of 24°F in peak temperatures during an identical run.

Mishimoto thermostatic oil cooler kit alone

Starting Outlet Temperature: 191°F

Ending Outlet Temperature: 194°F

Peak Temperature: 197°F

And finally we have the new thermostatic version of this kit, functioning solely off the liquid-to-air heat exchanger. Efficiency and temperature drop are slightly less with the factory cooler no longer in use, although improvements over stock are still significant. We saw peak temperature drops of 18°F compared to the stock cooler setup.

So what does all this data tell us? It provides the opportunity for our customers to choose the product that will best fit their needs. If you prefer outright performance and live in a reasonably warm climate, our non-thermostatic kit will provide you with the biggest gains. If you live in a cooler environment and would like a thermostatic option that provides protection against over-cooling your oil, our thermostatic kit is the one for you. Both kits we offer provide great improvements compared to the stock setup and will be very beneficial for both street and track driving.

Thanks for following along with our development process, feel free to follow-up with any questions or comments!

Interested in purchasing our thermostatic WRX oil cooler? Check out our product page for more information!

Mishimoto Subaru WRX Oil Cooler Kit

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