Should i buy a hotter thermostat?

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my car is a 1997 pontiac grand am, 2.4l 4-cyl with 148k miles... filled with dexcool. it has the factory 180*f thermostat (IMO thats pretty cold, especially according to today's emissions standards). i would like to get a little better gas mileage out of the car though, and i have seen a 192 and 195*f thermostat for sale online. would slightly hotter engine temps hurt? i know... some may say "well it came that way from the factory so dont mess with it". i've had several high performance cars that i've put lower temperature thermostats into with no problems at all, so maybe it would also work the other way around...? the car is slow to reach operating temperature and rarely creeps above operating temperature even in the summer heat or in traffic, so overheating isn't a problem.
 
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Been working on imports most of my time, I'm a firm believer in factory spec'ed termostat (most of the time, I replace with factory OE'ed thermostat, and wouldn't even bother with aftermarkets).
 
I wouldn't change from the OE thermostat temperature. You could end up cracking a head, blowing a head gasket, wearing your water pump prematurely. This is assuming the right one is in there now and wasn't changed with a cooler one at some point. Your local dealership and many parts look-up catalogs can tell you.

Now assuming that 180oF is the spec'ed thermostat...

Hotter engine temps are usually better for emissions but there is no telling what you could be trading off changing to a hotter thermostat.

You could send your NOX levels through the roof with hotter cylinder temperatures which can create pre-ignition (pinging) problems and cause you to fail a yearly emissions test if you are required to have one.

Now, all those warnings aside if you want to try it and are ok with the risks above, I wouldn't go past a 192oF if your original one is a 180oF
 
Increasing the coolant temp may mean that the ignition timing has to be retarded, so much so that it may hurt MPG rather than help.

You will have to buy more expensive parts such as a performance exhaust to get more MPG.
 
They set it up that way for some reason.


I was trying to verify that this was a traditional outlet thermostat and not some early evolution of the inlet thermostat ..but there does seem to be some oddity to the way they're routing fluid flow. Probably just bypass(heater core) and a sensor port ..but it still looks strange.

housing
 
All the Saturnfans people keep saying you HAVE to replace your broken/old thermostats with 195 units (185 was from factory)

I had a 185 in my SL1, and I have a 195 in my SL2.. There is no real difference aside from the gauge reading slightly higher in the SL2. Mileage is good in both cars.

I'd just use the OEM stat unless your mileage sucks (ex. your tstat has failed open)
 
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the car is slow to reach operating temperature

Install a new thermostat of the original set point. Thermostats do wear out and sometimes get sluggish instead of just failing.

We don't know what hot spots are present inside the engine. GM's engineers might know that and designed that engine to have an average coolant outlet temperature at that safe setting.
 
I'm with Ken, it's possible theres some bias you don't know about to make some other part of the engine run at 195 when the rad outlet is at 180.
 
Run the 195 thermostat and FIND THAT OE FLAW.

I've played with thermostat temps trying to increase MPG. In the winter, your engine will probably prefer the hotter thermostat. In the summer, you risk failure.

The biggest issue with changing the thermostat is that you need to understand the programming in the ECU. Suddenly the engine is running hotter, and the A/F and timing are not where they should be for MPG, HP, or emissions. You risk throwing all out the window unless you can tune or trick for that thermostat.
 
Originally Posted By: Gary Allan
They set it up that way for some reason.


I was trying to verify that this was a traditional outlet thermostat and not some early evolution of the inlet thermostat ..but there does seem to be some oddity to the way they're routing fluid flow. Probably just bypass(heater core) and a sensor port ..but it still looks strange.


I agree.

The thermostat is in the inlet pipe that bends down under the oil pan. The water outlet on the head, shown in that picture, is empty on the 2.4L and on last couple of years of the related 2.3L Quad 4.

Another possible theory is perhaps the cooler stat was needed to keep the head temp low enough to still avoid having to fit that engine with an EGR system.
 
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