Why do you think that the stock t-stat is not optimal?

Heath

 

Because all the vehicles I have previously owned had at least a 180 degree T-stat, and a couple even had 190-degree ones. From what I understand, keeping the engine at a slightly warmer temp will help the performance and produce lower HC and CO emissions. it may even help mileage; the extra NOX emissions that may result would be reduced by the EGR system, which is on these vehicles, anyway. Maybe Nissan recommends a 170-degree T-stat to prevent overheating while towing trailers?
My main reason for going 180, though, is to attempt to increase the heater temp; in my truck itis a little weak, and I usually don't tow anything.

Val
'02 XE

 

I would hesitate to second guess Nissan's engineers - but it's your truck. If there were no downside or a greater advantage to a hotter thermostat, I feel sure they would have specified one. What engineering team wouldn't want better emissions and better performance?

I would also be concerned about creating spark knock with a hotter engine - which I suspect they would address by enriching the fuel mixture. If your thermostat is the original, keep in mind that it's about 8 years old, and the seal around the seat is probably shot - so it's probably not warming up as quickly, or maintaining normal temperature in very cold weather.

Heath

 

Heath,
I have only had the truck one month, but that makes perfect sense; from what I see, looks like the coolant was never changed by the previous two owners of my truck; the coolant is brownish in color and I am getting ready to drain, flush, and refill anyway. My thinking was to replace the thermostat while the system was empty and avoid doing the job twice.
Right now, the engine rises to normal temp (temp gage needle exactly in middle) in 1.5 miles from cold and stays there no matter how long the trip is.
So, it looks like the thermostat is doing its job as designed.
And, now that I have the Haynes shop manual, looks like replacing the T-stat is also another knucle buster; so, I'll dispense changing the T-stat and just do a good coolant flush and see if the heater performance improves.

Cheers,
Val in FL

 

You might also investigate the condition of the heater core. Could be partially blocked or clogged.

 

Thanks you all for the tips. I drained, flushed and refilled the cooling system with new coolant, bled the air out, and now I have 140 degrees at the center vent without even the blower running. Definitely hotter now, about 10 degrees more than before. I am satisfied,

Val in FL