Which are, in general, a very bad idea for our trucks because there's a pretty good chance that the PCM will bark about it and keep the controls in open loop mode, thrashing fuel economy, performance, and emissions all in one swell foop.

 

I disagree. Just because your tstat opens at 170 doesn't mean your engine temp stays at 170. It all comes down to wether you use your truck as a daily driver or a work horse. I see no benefit in 170 tstat on a daily driver, but if you plan on towing heavy loads, it's quite beneficial.

Let's say you are towing at 80% your book max payload or 11,000 lbs. in hot weather, up a hill. With a 190 tstat, your engine will start cooling effectively at 190 degrees, which means that your engine can quickly heat to 230 and over, not good at all. But if you had a 170 tstat, you will start cooling at 170 and your engine will stay at lets say 210-215. Don't forget that the coolant running thru the radiator will also be a bit colder with 170, which would make it easier to dissipate the heat.

Right here alone the daily-driver loss of the 0.5 MPG for your engine running cooler has paid off. When you do that on a daily/weekly basis, it's quite understandable why people beef up their cooling more, especially on these 10+ year-old trucks.

P.S. I am not sure what you mean by "performance", but when I bought a V-10 emissions were the last thing on my mind and if I wanted fuel economy I would've bought a Prius Kidding, of course, but reality is that it's down right funny when people go through hoops trying to squeeze an extra 1/MPG from a 10/MPG truck. That's like buying a $100 bottle of wine, then saving the bottle for the 10 cents refund

 

What I mean is that the engine will not make its best power when the PCM is in open loop mode.

Not really. It's more like the gas station where you already buy your fuel keeping track of your purchases and giving you every 11th fill-up for free. If you'd force them to take your money anyway, well, that's your choice.

 

ok thanks guys i found it there was a hose disconnected from the air box i reconnected it and no smell thanks guys and yes im hoping to save the engine life rather than .1 mpg the mpg already suck plus its a truck!

 

I have my doubts that a 180 thermostat will cause a drop of .1 MPG.
The main reason for the higher operating temperature of the engines now days is emissions.

 

DING DING DING!!!! We HAVE a Winna! Emissions are indeed the motivation for higher operating temps we see on cars/trucks these days.

I also doubt the benefit of a lower temp thermostat if using your truck for 'heavy' duty. The cooling system was designed to keep the engine within an acceptable range, even at max payload. Sticking a 170 stat in, WILL give the PCM trouble. UNLESS you have a custom tune that takes it into account. The scenario given is NOT any kind of proof or evidence that the lower temp is going to help you. Keep in mind, the rate of temperature change, is DIRECTLY proportional to the DIFFERENCE in temps between two mediums. So, while the 190 degree stat, WILL have a higher initial temp when it leaves the engine, it will also shed that heat FASTER once it hits the radiator. If your truck is getting hot/overheating when under load, you need to have a look at your cooling system, and find out WHY. Putting a bandaid fix lower temp stat in there is NOT the answer. There IS such a thing as "too low".

With the computer controlled engines these days, what used to be a trivial change, that would eek a bit more power/longevity out of your engine, has become a stumbling block, that, if not done with some care, and forethought, can actually cause you more problems, than you think you are solving. The 180 stat probably really isn't a bad idea. Although, even that, on some of the later years, will cause the PCM to set a code.

 

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Is it really emissions related? Or was it for better fuel atomization = gained power. Reason I ask is... Why on earth would older cars have 195's then when you says the bolded? Key words... "Cars these days". I've replaced thermostats in a 74 vette, and a 66 stang... both of which were pre-emissions and both came with an OE 195. Your more than welcome to check Napa to verify. Your thoughts?

 

Running the engine cooler is actually better for power. (and worse for emissions) Cooler air is denser, and has a higher oxygen content.. so, while the fuel may atomize better at higher temps, you have less oxy to play with....

The 'emissions' craze started back in the mid to late 70's..... and got REALLY bad toward the end... back when there was more emissions equipment under the hood, than there was engine.... It was concern before then, but, not so much so. Was emissions the ONLY reason for running the 'higher' temp? Probably not, but, it was right up there on the list.

 

Well, unless someone with actual knowledge of the PCM workings pitches in, we will never know if the PCM actually adjusts the fuel between an engine running at 170 degrees and one at 190. I know that the PCM will throw a code if it runs "too cool" for a while, but at the same time I have never been able to find out where Chrysler defines "normal operating temperature" in actual numbers. Unless you got a code that the engine is running too cool, your PCM will not operate in open mode all the time. We are not comparing cold vs. hot engines, but 170 degrees vs. 190, i.e. both engines are pretty hot at this point.

Not true. Here is what Chrysler says:

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