I too would only run the 87 degree one but you have the thermostat
operation a little wrong. It is not an on/off switch for coolant flow.
It merely begins to open at the specified temp and opens wider and wider
as it gets hotter. Bentley page 19.11 has the operating range given. Not
fully open until 105 C degrees.

Mark

Dave Mcneely wrote:
>
>
> What the thermostat does physically is remain closed (no coolant flow) when the temperature is cooler than the set temperature, 80 or 87 C.  At the set temperature, it opens, allowing coolant flow.  It plays no role whatsoever in getting the coolant temperature to drop.  It will stay closed until the set temperature is reached, open, and remain open unless the temperature drops below the set temperature.  With the engine running in summer that is unlikely.  If the engine is overheating in summer (temperature running above 87 C), the thermostat might be stuck closed (not likely), but an 80 C thermostat will not make it run cooler if other causes are at fault (most likely).  Check the fan, the radiator, and so on.
>
> Given that the engine is engineered for 87 C, it should run at that temperature.
>
> mcneely
>