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Coolant, and motor oil, temperatures

General Tuning Discussion

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Ben mentioned in a couple of webinars that a thermostat cooler than stock would improve the tune. But for how much and what kind of influence can it have?

Looks like we’re stuck on the “what’s the best temp range and why.” I don’t know the answer but Davidv’s suggestion makes sense to me.

For ECT, look up OEM ECU’s algorithm and when they start to pull timing. I believe my OEM S2000 ECU starts to pull timing in the the 190>200F range. Fans kick on between 207F-212F. Based on that alone I’m going with me wanting water temps below 90C.

For oil there are some nice myth busting videos on YouTube THE DRIVE channel:


Sounds like 200F is where it becomes really effective and 212F is where the oil starts shine shine. Anything above 212F it start to thin out.

So my theory is:

Coolant: 85C-90C

Oil: 90C-100C

Hi Edward,

There aren't a lot of absolutes when it comes to oil and coolant temperatures and a lot will come down to the oil you're running and what you're trying to achieve. Many OE manufacturers for example are purposely running the engines coolant temperature up around 100 deg C as there can be some small improvements in fuel economy. From a performance standpoint a hotter coolant temperature can make the engine more prone to knock so i prefer to target around 80-85 deg C. The oil temperature is equally important and it can be a problem if it's too hot (because it starts to lose its ability to lubricate), or too cold (because it can't get rid of deposits and impurities that naturally end up in the oil). I like to run the oil between about 100 and 120 deg C on the track for a good quality full synthetic. This is where the thermostatic bypass comes in as it maintains reasonable oil temp when you're on the street but still allows for sufficient cooling via the oil cooler on the track.

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