So, one thing I've noticed while reading around on this forum is that there'* an overwhelming consensus that a colder-than-stock thermostat will improve performance, wear characteristics, etc. Most opt for the 180 degree version and some have even gone as low as 160.

I propose the following: colder thermostats may lower performance and increase wear.

Now, this is a delicate subject...there are many variables to consider. But:

While colder air means more power, hotter combustion chamber temperatures mean better thermal efficiency and more power produced (less energy goes into heat loss).

Hotter temperatures decrease the life of engine oil...but also decrease engine wear when oil life isn't taken into account (think about cold starts).



Of course, higher horsepower engines may need a lower temperature 'stat to keep from overheating, so this is aimed at stock N/A cars.

Thoughts?

I went to a 180 T-stat on my 1998 n/a L36 primarily to do everything possible to reduce operating temperatures and prevent UIM melting, not for any performance gains.

Even if this "mod" has the potential to shorten engine life (which I highly doubt), I expect the engine will still outlast the transmission by a large margin.

I'm a bit torn on the topic as to whether or not a 180 will keep the UIM from having issues, this is caused by the EGR tube, lower exhaust temps would prevent this from happening but theres not an easy way to accomplish this.

As far as intake gaskets failing, I'm 100% convinced that a 180 will help prevent the gaskets from dying as quick.

I will argue that a 180* will NOT lose fuel economy. on a 300 mile trip I used 9.9 gallons on the SSEi and I also had a 32mpg FLAT highway trip on my old L27 3800 powered Olds 88.

Sorry, but you would be mistaken.

The only reason the auto makers go to higher temp t-stats is for emissions purposes. It has no effect on wear and hurts the engines potential power output. In stock trim, the engine is running a bit on the lean side with a higher than optimal combustion chamber temp. This keeps the exhaust gas temps up so the catalytic converter can function better. EGR is used to cool down the combustion chamber if things get out of hand faster than the radiator can knock the temp back down to the 195 range.

You didn't start seeing 195 T-stats until the introduction of unleaded gasoline and catalytic converters. Before then, engine temps in the 160 to 180 range were the norm.

Well put Curt.. couldn't have said it better myself.

LHS, I get 32mpg in the Zilla at 70mph on the freeway with a 160 degree thermostat. I think it'* doing just fine.

I have a 160 T-stat and my mileage sucks.... (20mpg)


although it could be the gearing....

or the power....

or the fact that i eat tires for breakfast stop light to stop light....


nope I think its the thermostat...

Another benefit of the lower temperature thermostat that is often overlooked - cooler transmission temperatures. Since the transmission fluid is cooled in the radiator, a cooler running radiator keeps the transmission fluid cooler. The 4T60E does not like heat - it is the number 1 cause of transmission failures.

My engineering friends have told me, (and I believe them) that higher operating engine temperatures should produce better efficiencies. But theory and practice are two different things, and engine oil and transmission fluid at 180 work better and last longer than they do at 200.

Are you saying that hotter temps due to a 195 stat will thin the oil quicker over time and allow for more protection on cold starts?

I wouldn't say that'* reason to keep a 195. If you wanted more protection at cold starts, use 5W as opposed to 10W (especially in winter), and/or switch to synthetic oil, and keep the 180 in for more protection while you are driving, when you need the stat most.

i really doubt 15 degrees F will make a huge difference in fuel economy or life of the engine itself, other than helping prevent the intake gasket failures etc...
and that also is very true, so i think it is worth it to sacrifice a little bit of possible fuel economy and emissions control to prevent failure of those vital parts