...why?

 

from the way i understand it if u dont tune for the 160 tstat that is where u lose the mpg. the pcm thinks the truck is cold and is constantly trying to warm up making it run rich and as a result the loss of mpg, but if tuned for it the mpg loss isnt there.

 

BMW even goes as far as controlling the thermostat to open and close so they can vary engine temperature depending on driving conditions

 

has to do with the warm up mode and effiecent fueling

 

FWIW, I have a 160* stat and efans, they're set to come on at 180* and off at 173*. The truck consistently runs around 175-179*, and my PCM has been tuned for it, so my MPG hasn't suffered. With the factory stat and clutch fan, the truck ran between 195*-203*, depending on weather, and with a 180* stat and clutch fan, the temp would range anywhere from 188ish to up to 203*. (these numbers are logged with an AutoXray Scan tool). Another thing that I have noticed: with the cooler stat, my trans temps usually stay around 160ish according to the factory guage (Denali cluster), whereas they used to be up above the 200 mark with the 195/180 stats.

As for fueling and efficiency, I believe that closed loop begins around 137* or something like that, but I'm not 100* sure.

If the cooler stat will allow for more ignition timing before detonation begins, combined with cooler trans temps, and can be tuned for, I really don't see a downside. Some folks may say that the metals of the engine won't fully expand, and others will argue that the oil will not get warm enough to burn off moisture...I don't have hard facts to argue against that, just my personal experience (and an oil catch can that seems to catch any moisture that occurs in my oil before it has a chance to be burned off anyway). JMHO

 

I would say something like 75% of all engine wear occurs during startup and warmup over a stock automobile engines lifetime with good maintenance practices kept up. This being said, the Gen III engines out of our trucks were designed to run at a specific temp for optimal life and efficiency (well at least emmissions wise anyway) Yes, there is the metals expanding at different rates argument, this has more to do with initial low temp warmup though, aluminum pistons expand much faster than that iron block does when warming up, but some tolerances were built in, still you shouldn't run the **** out of it cold. But.. have you ever measured a piston, notice that it is actually slightly egg shaped, not perfectly round until it was brought up to its engineered operating temp. Do you want to pump something out-of-round up and down in a round hole at 6000plus times a minute? (Sounds like fun ) This is kinda the reason i believe running truly colder could honestly be harder on an engine not built to run there. Also as stated by other folks ithink there may be a problem with flashing off unwanted fluids from the oil in our daily warm-up-cool-down drivers at 160, maybe i'm wrong but water boils or steams off closer to 200 than 160 doesn't it? I cannot however disagree with drastically cooler engine temps you to run more timing and make better power, but will it come at a cost, only time can tell i guess? As far as an aftermarket stat goes, ithink your safest bet would be to go with something a little milder of a change, i went to a 180, big whoop right, but it got me away from some detonation problems i was having with FI setup.

Theres my bias!

 

^ What he said.

 

With my 160 stat I run right at 180-185 in most texas weather, in the summer I saw 195 a couple times.

-Lurius

 

Why not just tune the truck to have the fans come on sooner? The thermostats don't do all that much... as many say, with just the stat in you don't even come close to 160*. Just tune the fans to kick in earlier (if you have e-fans), and you'll be fine.

 

If your 160 stat opens and your engine runs anywhere different than 160 your cooling system isn't doing a good job