I've got a new thermostat from bursons, $23... nissan wanted $40 and repco wanted $55!!!
If your temp gauge is not close to the middle, or over 1/3rd almost all the time then its not running at the right temperature, which can affect your fuel economy because the ECU dumps more fuel in.
My fuel light does not work, globe is good, so it must be the sender in the fuel tank. Previous owner ran it till it stopped, light never came on... 647km to the tank (not sure how many litres). Because we all know km travelled, stated without an idea of how many litres have been consumed is useless.