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Old 08-28-2012, 04:42 PM   #8 (permalink)
DR_
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Quote:
Originally Posted by ChrisSlicks View Post
Coolant thermostat starts opening at 180F but isn't fully open until 200F by my measurements (reading coolant temp on OBDII). Cooling fan kicks on at around 220F.

The viscosity of 5W30 at 180F is approximately twice that of oil at 210F. It isn't going to hurt anything but you are losing some efficiency.
Good info. My thermostat seems to fully open a little sooner at about 196f. Also what numbers are using to come up with twice as thick at 210f? The SAE viscosity curve charts I've seen show about 15 cSt at 180f and 10.5 cSt at 210f but good synthetics should be much closer. I'm not a chemical or mechanical engineer (my wife is a CE), but I'm interested in the subject.
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