Lower Temp Thermostats. Whats the deal?
 

What is the purpose of a lower temperature thermostat and what are the pro's/con's of fitting one?

Ive recently been reading into people fitting lower temperature thermostats in their cars/Scoobys and wanted to make a discussion about them.

First of all, is the following accurate in terms of how a thermostat works in a car?

* Car is started from cold and thermostat is currently closed.
* Engine starts to warm up.
* Coolant temperature in the engine block increases and reaches xxx degree's.
* Thermostat opens at xxx degree's and coolant circulates through the radiator.
* Thermostat remains open until coolant temperature drops and closes again. Eg, when engine is turned off.

Am I also right in thinking that once a thermostat reaches its opening temperature, it will not close fully or narrow its flow because the engines normal operating temperature is higher than the thermostats. For example, the thermostat opens at 80 degrees but the engine's normal operating temperature is 90 degree's (or maybe more with 'spirited' driving) so the thermostat will not begin to close again until it drops to 80 degrees which probably means the engine is turned off and slowly cooling down.

With this in mind, back to the original question...What is the purpose of a lower temp thermostat?

Does it simply open sooner and circulate through the radiator meaning the engine takes longer to reach normal operating temperature?

Yes pretty much :) Roger Clarks sales pitch is...

You have various options. OEM is 78, Zerosports is 71 and Cosworth is 68 to name just a few. With the 68 and an oil cooler you will struggle to reach consistent operating temps and will run perhaps too cool as a regular drive. The 71 I ran in 2 of my Subarus was fantastic and it ran much cooler across the usage than the OEM Stat. I am convinced my 2.5 ran without issue as I fitted the cooler stat at 7k miles :)

It's also important to point out that the 'uprated' stats are designed to fail in the open position to avoid over heating, whereas the OEM stats are not :)

Thanks for info 53.

With a lower temp thermostat installed does the engine temperature change when driving or does it stay the same like if you had an OEM one fitted?

Mine ran consistently cooler and the idle temps are certainly lower. I had some numbers I posted ages ago when this was discussed before I will have a search :) On my S202 with the oil cooler and 68 stat, it was so effective it was hard to keep it over 80 degrees. That's on the road and I only really use the 202 on track which is fine :)

Here you go :)

Does it have a negative effect on the ECU/Performance if the temperature fluctuates or if it stays steady at a temperature lower than OEM?

Not if it's in normal op temps. If it struggles to maintain 80 say it will constantly think it's in warm up and have fuel implications and maybe AVCS operating issues not sure.

I've gone for a 70c rcm one, mainly because it was slightly cheaper and a cossy 68c one may have been too cool.
(You been reading my thread op :D)

I bought another Cosworth one for my V2 as is doesn't have an oil cooler and is only going to be a road car :)

Hmmm interesting, im toying with fitting an oil cooler as im seeing oil temps of 95 - 100 on spiritied driving, im wondering if a 71d cooling stat would reduce oil temp also by 5 or 10 degrees ?

My car is a little too efficient on the mway with a zerosports stat and an oil cooler both oil and water can dip as low as 71 degrees. Locally however it maintains perfect 80c, rig if its a 2 litre you may get it down 5 degrees but the ideal is about 85c for oil temp

Ok cheers bud, just seen the prices of the stats, £75 for a cosworth one or £59 for an RCM one, Ouch !

Think i will fit an oil cooler

cheers

Not seen your thread you mention, have you got a link?

EDIT: Do peeps use gauges to monitor their temps or gadgets like Scangauge?

Lol, you got to pay to play.
On icp direct web, the cosworth ones comes in at £72 delivered with the 10% user discount or Alyn at AS can do the rcm one at £57.

If i could guarantee it would lower my oil temps as well id go for it, but running my coolant at 71 or 77 degrees doesnt worry me too much, its watching my oil temp hit 100 on a hot day that scares me lol and an oil cooler i can get for around the same money which i think will benefit me more, i was jusy hoping a lower stat would cure my oil temps as its alot easier to fit than an oil cooler

cheers

Do you know what the ideal running temp is on a 2.5 forged engine ?

Scangauge II is excellent on UK cars but sadly won't read JDMs :(

100C is nothing to worry about with oil, in fact it's ideal. Assuming you are using a good 5w-40 or 10w-40, that will be fine up to about 130C or slightly higher peaks. Under about 80C, not all of the additives in the oil are doing their job properly and the oil is not flowing as well as it should.

If you're only getting to 100C, don't fit an oil cooler, it's not going to help with protection.

Cheers

Tim

Ok bud thanks for the info , I'm running a 10/50 Fuchs Titan pro S oil

Cheers

Hi

In that case, it's fine up to about 140-150C.

Cheers

Tim

That's interesting.
Where does that information come from?
Is it your own findings or manufacturer's specs?
Is it real world usage (i.e. on track) or is it laboratory environment testing?
I'm genuinely interested.

Hi

That was from John Rowland of Fuchs a few years ago, but the oil hasn't changed.

I think it was a cross of lab testing and his own use (although not sure of the vehicle it was in).

Cheers

Tim

Total agree with oilman. No need to fit an oil cooler. And if you see 130degrees with a high quality oil, not a problem. Start to get higher than that regularly then that is when you need a cooler.

My oil temp sits at 130degrees on track, with a 16 row cooler fitted with proper fabrication so the air flows straight through and is pushed out the back. (it is a wet system with a baffled sump and a 11mm oil pump)

Harvey used to say to me he never worried until about 140degrees....he used to run Royal Purple.

I have also run Fuchs Pro S 10/50 at 130/140 degrees for about 15mins flat out with no problems.

Cheers
Steve

Thanks for the reply Tim :thumb:

Got my stat today
https://cimg1.ibsrv.net/gimg/www.sco...ca7ea3a62.jpeg

Isn't the car going to be cold in the winter ( via heater matrix I mean ) , with my oem stat it takes long enough to warm up in the cabin lol

Just on the oil temp thing.....mk1 golf gti manual used to state if oil temp hits 140 to slow down/allow car to cool...and thats going back to early 80's!

As for the cooler stats surely the car will still get to its operating temp eventually? Std stat may be 78 but car operating temp is around 90 and fans kick in at 96....or so it did on my hawk sti using the psi3 to monitor

Interesting read


http://www.iwsti.com/forums/built-motor-discussion/197704-truth-about-thermostats-don-t-get-caught-hype.html