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I Seem to be running very cool, according to dash reading anyway. This has coincided with an increase in fuel consumption (10%-ish) and a seat of the pants guestimate that performance is dulled. Also aircon is not as warm as I remember at 22degrees. I think that the stat has failed open.
Now the rub - if the compensation for cool running is overfuelling is this likely to degrade the oil. I ask because I have heared of cases in carb fuelled cars with sticking chokes where the engine has suffered terminal damage.
I'm due a service in 1K miles and wonder if the stat change will wait till then
 

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It could be a stat stuck open; to check this start the car and let it idle. As the temp initially rises, you shoudln't feel any warm water in the top rad hose next to the rad. If you do, then the stat is probably stuck.

Lower temp coolants will increase the MPG, but I would say they wouldn't go so far as the massive overfuelling that you can get in carb cars, because you've still got the balancing effects of the lambda sensor and DI monitoring, which actually enable the engine to use as little fuel a possible during warm up.
 

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Lower temp coolants will increase the MPG[/b]
Obviously, from the context, this is intended to mean 'will reduce the fuel consumption' (not 'MPG').

Lower coolant temps will reduce MPG, which means less MPG and increased fuel consumption.

Confused.. you should be


The reduction in MPG is dramatic for a 10 to 20C drop in outside air temp - as indicated in the Saab 9000 User Handbook. It contains some interesting charts. With UK temps around 2 to 10C recently, my temp gauge is often sat at the 1/3 off cold position - and economy drops several mpg even when engine is up to running temp.

At this time of year, it's normal for a few threads to appear with concerned 9000 owners noting radical drop in fuel consumption and unnecessarily fearing a mechanical/electrical problem!

I think my thermostat is OK, but top hose temp is a good test so will check it out too - thanks Bubbles.
 

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Originally posted by Paul D:
[qb] QUOTE
Lower temp coolants will increase the MPG[/b]
Obviously, from the context, this is intended to mean 'will reduce the fuel consumption' (not 'MPG').

Lower coolant temps will reduce MPG, which means less MPG and increased fuel consumption.[/qb][/b][/quote] Fingers quicker than brain...
 
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