I just installed an aftermarket water temp gauge and it appears that my coolant is running at 180 degrees once the truck is warmed up. I think that I saw somewhere that the factory thermostat should open at 195 and I know that the previous owner put a thermostat in before he sold it to me. Does anyone know what the OEM thermostat temp rating should be? Also, would having the engine run cooler than it was designed to affect performance/MPG?

 

What year, what engine?

 

This, but either way I think all the engines have 195* thermostats.

 

Sorry, forgot to include that...1992 4.9L.

Any thoughts on impact on performance, longevity, and fuel efficiency with the 180 thermostat?

I read somewhere that the computer will always run a rich air/fuel mixture with a 180 stat. True?

 

Computers and fuel injection like the higher temp. should be 195' True on running rich air/fuel ratio

 

My 1991 pickup with 302 motor had a factory 192 degrees in it when replaced it

 

You should be fine with the 180, running cooler might even improve gas mileage.

Ive read that the 195er was installed in the trucks headed to the emissions states like California.

(Some guys are even running 160's and getting gas mileage in the low to mid 20's)

 

From what I have read it seems that running at 180 will cause it to run rich as it will always be in "warm-up" mode

 

Not to get off track of this Thread. Last year when I had to change my water pump on my 4.9L I got a new thermostat while I was picking up the water pump. I told the parts guy i wanted the standard thermostat. The one they gave me was a 180 degree. I didn't install it 'yet', and put it in my tool box.

Could there be a reason for the parts people pushing the 180 degree thermostat? Maybe from Ford? Just wondering

 

Unless you have a specialized application, you always want to run it at the OE recommended temp. Most of that time it is 192-195. The trucks are designed to run at those temperatures and will give the best performance/fuel economy within that range.

Using a 180 would almost certainly result in lowered mpg's.