Which thermostat, 180 or 195 degrees ?
 

RockAuto lists two thermostats for a 99 4.3L Silverado with different setpoints: 180 and 195 degrees. Will they make the engine perform differently? Should I just get both ($6 each) and do a trial run with each? Are there other system components that are expecting one or the other? Does the choice depend on the climate where I drive the truck? What performance differences should I expect? Any help or links appreciated.

Stant says that "OE recommended temperatures should be used in nearly all situation"

ABC's of Thermostats - CONSUMER PRODUCTS - Stant

On another page, Stant is quoted:
Replacement Thermostats
The temperature rating of a replacement thermostat must be the correct one for the application because of the adverse affects the wrong thermostat can have on drivability, engine performance and emissions.
The temperature rating specified by the car manufacturer is especially important in many 1981 and newer vehicles because the onboard computer monitors coolant temperature through a coolant sensor to control fuel enrichment, spark timing and operation of the EGR valve. Even on vehicles without computers, thermal vacuum switches that react to a specific coolant temperature are often used to open and close various vacuum circuits that regulate fuel enrichment, timing and EGR. If a colder thermostat is installed, the coolant may never get hot enough to trigger the appropriate control functions or to allow a computer system to go into “closed loop”. Too hot a thermostat can also interfere with the proper operation of engine controls, and increase the engine’s operating temperature to the point where it may experience detonation (spark knock).


http://www.crankshaftcoalition.com/w...tats_explained


Some additional explanations:
Low Temp Thermostats: What’s the Advantage? | Tuner University


And the google search link
https://www.google.com/search?hl=en&...erature+rating

Kind of seems that the choice is fairly inconsequential as long as the designed operating temperature of the engine is around 210 degrees or higher. So, how does one find out the designed operating temperature for the engine, a 1999 4.3L in a Silverado?

I did some searching and found that it seems to be somewhat unanimous that the 195 stat is the standard. And a normal operating temp for a 4.3L is between 165 at the low end, and 200 at the top.
Apparently the 4.3L is renowned for blowing head gaskets, the column culprit for this engine failure is high engine temperatures