Thermostat opening temp opinions

[hgeranium]

I understand that the typical operating temperature for a Renix 4.0 is ~210 aka right in the middle of the gauge. I've never had to replace the thermostat yet, but as long as I've had the truck, my temp gauge has always stuck around that first quarter mark at operating temp. I think it's about 160. On rockauto I see that there's a 160 degree alternate option thermostat. I assume there's a good chance PO put one of those in there. Unless my instrument panel ground is causing it to be finnicky, although I only notice a clear ground issue with the battery voltage, so I think it's OK.

 

My question is: what thermostat temperatures do y'all like to run? I live in South Texas so, in the summer, the cooler operating temperature is appreciated, but I'm wondering if there are any benefits/downsides to any of the other (including OE) temp options. 

[89 MJ]

I’d verify the temp with an infrared gun, but it could be that it was swapped to a 160. 
 

Being that it was designed to have a 195* thermostat, it would get slightly better gas mileage. It might also run a little bit better. 
 

With how spotty the quality seems to be with new thermostats, if the installed one seems to be working fine, I’d stick with it. If you have any troubles with it, I’d run a 195*. 

[hgeranium]

1 minute ago, 89 MJ said:

Being that it was designed to have a 195* thermostat, it would get slightly better gas mileage.

Yeah that would partially explain why my mpgs are so shoddy compared to a lot of the other guys on CC (things are looking much better after the new fuel pump though!). I'm thinking in the past the fan clutch was starting to go out (or maybe he just didn't know how to burp the cooling system lol), so instead of replacing it, the previous owner put in a low temp thermostat and swapped the electric fan to a key-on situation rather than temp-based.

 

  I'm just glad he kept the original AMC housing instead of replacing it with a crappy aluminum unit for no reason when putting on the thermostat.

[89 MJ]

Seems like everyone has a PO story like that lol. 
The thermostat is definitely a factor. Daily driving these trucks in town will kill mileage too. My truck is 14-15mpg in town and will only get 20 or so cruising on the interstate for the entire tank. 

[75sv1]

I run a 195-197 F thermostats. I have been running 205 to 210. MPG is discussion on its own. Some say a 205F Thermostat gets better MPG. Also, a lot of this depends on ambient air temp. I have had a few thermostats stuck open or even come apart. 

[watchamakalit]

Don't trust the dash gauges to be accurate. I thought my truck was running cold for years (guage said 165-170 hot).  Thanks to a rem unit and some further investigation I found out the problem is all in guage accuracy.  Truck runs properly and at the correct operating temps.  Could have saved me a couple tstats and a lot of head scratching to start with the gauge. 

[hgeranium]

53 minutes ago, watchamakalit said:

Don't trust the dash gauges to be accurate. I thought my truck was running cold for years (guage said 165-170 hot).  Thanks to a rem unit and some further investigation I found out the problem is all in guage accuracy.  Truck runs properly and at the correct operating temps.  Could have saved me a couple tstats and a lot of head scratching to start with the gauge. 

What's interesting is that, when unplugging the e fan (PO has it to key-on), I was sitting around 195-210 at operating temp. But yeah I have no reason to trust it until I upgrade the instrument panel ground