13 hours ago, Captain Obvious said:

How do you know?   

I have an infrared thermometer and checked the temp at the radiator and thermostat housing.  Ran cooler with the new sensor and shroud.   

So a new shroud could explain a cooler temp at the radiator. A new sensor wouldn't make any thing cooler but may make the gauge show different.
The stock sensor is located at the lower part of the thermostat housing. Is it picking up the coolant temp from the front of the head?
If that is the case the thermostat then opens when temp reaches 160 and allows cool water to enter. Correct? What good does putting a 160 degree thermostat do? Sounds to low! Is there an optimum operating temp for these stock engines?
Thoughts any body!


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The appropriate OEM Nissan thermostat is available online.

My suggestion: Try one.

I replaced my radiator with a 3 row and replaced my thermostat with a factory 180 degree.  Before I made the change, my gauge would go all over the place.  Now it gets to temp and stays there regardless of highway or city driving or ambient temp.  Personally, I always thought the 2 row radiator was inadequate.  One of my previous owners may have thought they were doing the car a favor by installing a 160 degree thermostat.  Factory was 180.

I also must confess my coolant looked like my morning coffee.  I flushed, backflushed, etc, etc, probably 3 - 4 times this summer to get it cleaned out.  I am sure that helped.