So while we're on the topic, how low is too low for a t-stat to go? I've got the OEM 185* in right now as I didn't like how hot the car ran in the summer. The coolant would still get to 215* if it idled long enough (isn't that where the stock fans come on?) but starting with cooler fluid lengthened that window. Now that cooler winter weather is here, I never see the temp go over 188* and it's 186* when cruising. Should I put the OEM 195 t-stat back in now that the heater core is taking more of the thermal load?