Quote:
Originally Posted by JFP in PA
OK, here goes: The thermostat sets the baseline minimum operating temp for the engine; it is the temperature the engine returns to when running at a steady state (road speed air flow across the radiators). Because of the convoluted design of the M96/97 cooling system, particularly the engine passages themselves, these engine's typically run a bit hotter than the temperature at which the thermostat opens. As the result, with the OEM stat opening at 186F, it is not unusual for the engine to run 210-215F at steady state on a fully instrumented 986 (forget what the dash gauge say, they are well known for being both woefully inaccurate and non linear). Because of the cooling system layout, at that temp the engine is actually much hotter in some internal areas, and as the oil is always hotter than the coolant (even though the engine uses a oil to water heat exchanger).
Changing to a 160F stat tends to lower the steady state coolant temp to around 175F, and more critically lowers the oil temps by over 25F, which the oil likes much better (UOA's before and after have shown the oil actually shows better parameters for longer distances between changes with the 160F stat). And on a base car, adding both the 160F stat and the "S" oil cooler (nearly twice the capacity of the base unit) improves the oil life even more. In essence, lowering the coolant and oil temps translates into improved life for both the oil and the engine.
And once and for all, cars with 160F stats do not warm up more slowly; in fact, the tend to warm up more quickly as the warmed coolant starts to flow sooner, not later.
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JFP,
Thank you for the explanation.
Have you instrumented the "steady state" temps you're speaking of?
Your explanation contradicts my understanding of the principles of thermo dynamics. If the car runs steady state of 210-215f with with a 186df thermostat it should run the same with 160df thermostat. Both thermostats will be wide open flowing fully. The engine produces the same amount of heat and the cooling system has the same capacity. "Turning the cooling system on sooner" should have no effect on the steady state operating temp.
As to the "once and for all" comment. I'm not talking about water temp,in the radiators, I'm talking about the block. As far as heat in the cabin, I was not aware that the thermostat controlled the flow to the heater core, that is uncommon in most cars. What i am concerned about what is important to engine longevity for cars operating in a 4 season environment, the oil temp. Adding 30df radiator coolant to an engine that has just gotten its recirculating engine coolant 160df is a recipe to slow the warm up to steady state temps... Like adding ice cubes to a pot of water that your trying to boil.
My contention all along has been that the only thing a low temp thermostat does is slow the time it takes for the engine to get to "steady state" and you've not changed my mind.
Those of you running low temp thermos: What changes are you seeing on your temperature readouts? Notoriously inaccurate or not, the gauge ought to at least be consistent in its inaccuracy (I mean there not made by Smiths or Lucas) and show a lower steady state operating temp if what JFP says is the case...even if the number is wrong.