The 06 FSM shows the auto and manual trans having different thermostats.
Manual opens at 169-174°F and is fully open at 194°F
Auto opens at 177-182°F and is fully open at 203°F

Anybody know why the manual gets a lower temp t-stat? Has there been any testing done showing the best temp for power vs gas mileage?
I feel my temps are way to high, It's not uncommon for me to see temps as high as 210° While cruising I generally see 195-199°

 

Lower temp for the manual? Perhaps Nissan feels the manuals will be driven harder and need to open the thermostat earlier to compensate. Just a guess.

BTW, 210° is no problem, your cooling system can handle a lot more. A 50/50 mix of coolant (ethylene glycol - commonly referred to as 'anti-freeze') and water boils at 265 deg. F and freezes at -34 deg. F (according to Prestone - who makes the stuff). This is with a 15 lb. radiator cap and cooling system in good condition.

Pressure in a cooling system raises the boiling point by about 2-3 degrees for every additional PSI in the system. The Infiniti 13 lb. radiator cap is 2 PSI less than the 15 lb. cap above, so the boiling point would be a bit lower - about 260 deg. F.

BTW, that pressure in the system is also the reason you don't remove a radiator cap when the engine is hot. If you remove the radiator cap from a really hot (e.g. 240 deg. F) cooling system the release of pressure will cause the coolant to instantly turn to steam that will burn you quite severely.

 

^^ Couldn't have said it any better myself.