Thermostat Choice

[RL 325i]

some of you might know I failed Smog because of extreme high NO measure.

I am already looking into getting a new cat, O2 sensor, plug, coolant, TB etc... pretty much a major tune up.

I notice that the temperature of the car after driving 30 minutes. it only reach 1/4 of the mark.

Someone I talked to suggested one of the high NO reading is because the engine runing too cold. He said my normal temp reading should be half mark. He suggested that I should replace a hotter Thermostat.
I am about to order it on line. they listed 3 temperatures. 71,75, and 80 degree. Which should I get to get my car run hotter.
Help pls.
Ron

[AdamF 88iS]

80*.

Get the car REALLY hot on the way to the smog check place. The hotter the catalyic converter is, the better. High NOx on these cars is a sign that the cat is going.

[AdironRider]

80 degree x 2. No need for anything else with a lower temp.