August members of this site, I ask for your opinion. I am going to replace the T-stat in my '90 IROC with a 5.0l TPI engine. It currently has a 160 degree t-stat in it, and now that the air dam is in place, my car very rarely if ever sees the high side of the 160 temp mark. Now, although I am always very wary about messing with something that is working......I had read many posts on various Camaro boards that state the engine temp needs to be above 175 or so to allow the computer to tell the engine that the car is warm vice cold. Sooooo....what T-stat would you recommend, a 180 or 195 degree T-stat?? The Haynes manual calls for a 195 degree one, but I don't want the car to get to darn hot.....though think my heat issue was solved with the addition of the air dam. So, what do you think??

 

Install a 180* thermostat. A 160* thermostat will take the engine a lot longer to get to Closed Loop and you won't get the best performance or gas mileage from your engine.

 

Put in the stock 195. Overall engine performance and optimum operation of emission equipment occurs at 195. Dropping the stat even 15 degrees will cause a loss in fuel economy. Many guys prefer the 180, it really depends on how much stop and go you do. I have used every stat and documented fuel economy. The best overall driveability occurs with the engine running at the temp the engineers designed it for.

 

I prefer 180*, what was the difference in fuel economy between 180* and 195* Danno? I am curious although it doesnt matter to me, I gotta fill up every 100 miles anyways

 

With my 180* thermostat and A/C on everyday, I fill up every 225 miles combined city highway driving. Without the A/C on I could go about 245 miles before fill up.

 

Did not notice much difference in stop and go because it was always close to stock temp. My once a year run to the shore with it I lost almost 4 mpg. That is highway type driving with full airflow to the rad so she was cool. What made me start to look into the problem with colder stats was that when I placed the ECM in the field service mode it indicated a rich mixture at the operating temp I normally ran at. To double check I used an oscilloscope and checked the O2 sensors output. It was always bouncing around .7-.8 volts indicating a richer than normal mixture. While there is much discussion about the ECM's ability to block learn to compensate for different operating parameters I am not convinced that it can optimize fuel delivery when you constantly have large temp swings. For example, if you run a 170 stat it will stay around that temp as long as you are moving above 45mph or so. Get in traffic, and she goes way up then starts to cool way down with air to the rad. This temp swing has to change fuel delivery. In my opinion a more stable operating temp results in better overall driveability.

 

I'm using a modified 195* with no temperature problems. I drilled 3 small holes in the top of the thermostat, to provide some flow before the big valve opens. You get a nice, progressive temperature ramp-up and no 'spikes' in heavy traffic.

 

Appreciate the inputs....after some thought, I put in a 195 degree T-stat.....and everything still runs way below the 220 mark, even with the car idling in the driveway for a half hour or so today in the heat (about 90 degrees)....I am getting over 225 miles per tank.....so everything now in my IROC is factory norm except for the fan switch (195 degree JET switch) and I will probably keep that one installed.....