I believe the theory goes that the pcm is programmed to adjust the a/f ratio after reading input from the coolant sensor (among others). When a pcm designed for an engine running at 195 sees that the coolant temp is only 180, it pushes more fuel to get the engine up to temp..thus (don't think I've ever used that word before lol) your mpg goes down due to using more fuel.

Whether this is true, or even a noticeable difference is up for debate. But..why run a 180 when there is no benefit over a stock 195? (assuming you are not running a tuner)

 

I run a 160(can't remember ) in my dodge dakota and pulled a leveled 60 foot by 12 foot wide mobile home down the road ( was just frame and wood floor left) and my temp still got up to the 195 mark but I was also pulling at 55 MPH and my little dakota didn't struggle at all! Love that truck and I got a manual to put behind my 5.2! Oh and my truck didn't throw any codes and I haven't seen my MPG change any from the 195 to the 160

 

Ive been searching and reading for the past four plus hours here, and it seems to me that going with a 180 degree thermostat and 3923 plugs, as well as a larger throttle body and exhaust will give you some nice gains in power. Right now I`m working on ordering all the parts needed as money allows. I will also be getting a tuner because my truck does have the death flash, but that won`t be until later in the year.


From what Ive read in other searches is that our trucks are tuned to make the most power with the coolant temperature at 182 degrees, and that the 195 degree thermostat is for emissions purposes only.

 

I have an SCT 9550 tuner but have not made my major engine mods yet (RV cam, new heads, roller rocker arms, performance intake, 408 stroker kit). I also purchased the tuner used and the tunes that came with it do not match my truck's setup. I went ahead and installed a 180 stat, new water pump, CSF 2969 all-aluminum radiator. I also removed all of my freeze plugs, dug out all of the silt/muck in the block's water jackets around the cylinders and re-install deep cup brass freeze plugs in the block and heads. I did all of this work to cut down on future cooling system issues, ensure that I have no issues when pulling a trailer and prep for future engine mods. I also feel running a 195 degree stat is more an emission thing and runs the engine too warm for my taste.

 

But here when its -40c plus windchill it is nice to be running warmer. Lol.

 

I fitted a 180°F Stant in anticipation of going to an SCT (Hemifever) tune... I saw a very slight improvement (not decrease) in MPG and power, but this was likely more due to the replacement of a very old timing chain, and nothing to do with the T'stat.

Then when going to the SCT tune, I got the extra get up and go.
I have a Wideband A/F gauge, and see no rich state in normal running at 180°F.

Cabin heating may take a little longer, but it is certainly adequate.

 

A 180° does NOT improve the cooling of (the 2nd Gen) engines. I went through this argument with the 180° crowd back when my 2nd Gen kept running hot -- "Oh, install a 180° thermostat and the truck will run cooler".

That is not correct.

 

To Gary-L


I have done a lot of searching and reading the past couple of days, and I`ve learned two things about the 5.9 engine that effect its performance or operation. 1) The plenum plate, dodge could have done a way better job in designing a plate that wouldn`t blow the gasket. 2) The original factory tune caused detonation/pinging under load in these engines, so dodge came out with a band aid fix with the death flash to reduce the timing, when the real problem was that these engines are running to hot and that caused the detonation/pinging problem a lot of people have with these engines.


So by swapping out the stock 195* thermostat and going with a set of spark plugs one heat range colder than stock makes a huge difference on these engines. With this set up people were noticing a bit more power and better gas mileage.


These are the facts, so believe what you want.

 

Uh...nope. Those aren't facts. Death flash was installed to cover up pinging due to a blown plenum gasket. Fix the plenum, get rid of the death flash (via an SCT tuner or similar).

Nothing to due with a thermostat...

 

+1 completely agreed!