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There is no correct thermostat, just like there is no correct intake, exhaust, turbo, etc when it comes to upgrading a car.

That's kind of like saying there is no correct fuel. Sure, you could fill your tank with diesel, but your car's going to run like crap, if at all.. There might not be a correct thermostat either, but if having a lower temp one is causing a CEL telling you that the coolant temp is too low, then you might be better off with a 180 degree one.

It could be a combination of the 160 degree thermostat and aluminum radiator that isn't allowing your engine to get up to proper operating temp.

 

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The way I figure fuel mileage is by recording how many miles I've gone since my last fill up. When the light comes on, fill up again. Then divide miles by gallons.. mpg.

 

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How is it hogwash? A lower temp T-Stat allows more coolant through engine because it opens earlier and closes later thus allowing more heat to be taken away, thus engine runs cooler... Yes the radiator helps lower coolant temps and is an important part but if the T-Stat doesn't open as much the engine WILL run hotter... At least thats how I understand it.

I think what he's getting at is that it doesn't really effect the normal operating temp. IIRC when I did some logging on the highway last summer my coolant temp was around 206 degrees, steady. So if I had a 160, 170, or 180 degree thermostat wouldn't really matter because all three should be wide open at that point.

 

[MainFrame]

Yea, OK, it doesn't keep the engine temps at 160*F or 180*F because of it's placement, down in the coolest part of the engine, and maybe isn't wide open cause the temps down there aren't as hot. But I would bet, if it was at the top of the engine where the coolant leaves and is the hottest it would keep the engine at 160*F or 180*F on average... So if Subaru put the T-Stat there it would be a hotter T-Stat than what they now recommend or the engine would run too cold... Again JMO as I see it.

The thermostat is really just there to expedite the warming process, not control the temperature. The efficiency of the radiator is the number one thing that determines the coolant temp. The thermostat acts like a cut off on the lower range, not allowing the coolant to circulate, so once the engine is up to operating temperature the thermostat should play no part (unless you're in a really cold environment, then it will continue to help keep the engine warm enough). And like what Trainrex was saying, changing when the fans kick on makes a difference too, but I doubt it does much while you're moving.


Wow.. I just had deja vu..

 

[MainFrame]

Yeah, I agree, coolant temp isn't that important. There are several people who track their cars on hot days and never have an issue over heating. I think even up to 220°F (104°C) is acceptable.. 190°F-210°F (88°C-99°C) should be a good safe range.


What's much more important is oil temperature.

 

[MainFrame]

Hmm.. I'm not sure, I've never really fooled with an automotive thermostat. I pretty much assumed that most are either open or closed, with little room in between. I would be tempted to pick on up and throw it in a pot on the stove with a candy thermometer... but I'm lazy.

 

[MainFrame]

the only reason a car has a thermostat in the first place is to allow it to warm up quickly. After it opens it pretty much stays open until the car is shut off and the coolant starts dropping blow the "full open" temp rating of the t-stat. The radiator and fans control over all engine temp.

That's pretty much my understanding.