2004 mercury mountaineer
 

I have a 2004 Mercury Mountaineer v6 and need to replace the theromstat. Trying to see what range i need for the theromstat to open fully. I've seen some that says 180 and 192 degrees. Just not sure on which one i should get. I really don't know if it is the theromstat but my temperature gauge stays below half and near cool. Could the theromastat be the problem?

Okay, so you are replacing the t-stat because you feel the Mt'neer is running too cool?

I say let it run cool. though you might want to make sure that the temp sender (coolant temp sensor) is still working (or just replace it, they're usually cheap parts).