Importance of thermostat?

[maxp]

I replaced my faulty thermostat this weekend, as the temperature needle would generally hover around 75-80 deg C instead of 90.

Obviously your engine is in danger of overheating if you have a stat that likes to stay closed, however mine had the opposite problem, meaning the engine coolant was generally running too 'cool'.

So, I was just wondering how beneficial this actually was to the car, i.e. what this now changes?

All I can think of is:
1 - The heaters will warm up abit sooner
2 - Very very marginal fuel savings

Anyone got any other disadvantages of an engine running too 'cool'?

 

[PaulTheo]

Potential increase in engine wear, poor heater and poor fuel consumption are the main points. My previous car would run very cool at higher speeds and fuel consumption was about 20% worse.

 

[s3dave]

They are designed to fail open for obvious reasons, i would say you should see a significant improvement in mpg

 

[Welly]

Constant over fuelling simply (and consequently poor fuel consumption as stated).

Over fuelling will not be doing your cat/s any good.

 

[Nilz]

Ive changed my stat recently and my fuel consumption is still pretty bad, is it worth changing the CTS as well, would that make a difference??