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Black on Black 1997 E420
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Discussion Starter #1 (Edited)
And based on the fact that your old one was stuck open, I'd bet you'll see a decent mileage improvement.
Greg
I believe my high engine temps are a result of a faulty thermostat. Even ran hot at 71F ambient temperature. Most times the A/C is off. I never realized the correlation between abnormally high engine temperatures and poor fuel economy b/c my mileage has been crap lately until I read the thermostat DIY. All fuel related maintenance items have been timely addressed. Could a bad thermostat cause my heater not to kick in, too? I replaced coolant 2 weeks ago and ran heater(on HI setting) to circulate fluid but air was cold with running compressor.
 

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Outstanding Contributor Always Remembered RIP
216 with everything. 2002 SL500 with everything. 2009 SL500 with everything.
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The correct engine tamp for that car should be in the 85c to 90c, the thermostat should open at 87c. If you car is running that cold the heater will always feel very cold by the time the water has passed through the heater matrix and blown. The fuel consumption will be very poor.

Sorry I do not do F on these things :)
 

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The correct engine tamp for that car should be in the 85c to 90c, the thermostat should open at 87c. If you car is running that cold the heater will always feel very cold by the time the water has passed through the heater matrix and blown. The fuel consumption will be very poor.

Sorry I do not do F on these things :)
Still posting Malc...good to see.
 

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E320/E250 Bluetec Ford F350 6.7l
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OP posted about higher temperatures, than normal. Those do not affect fuel consumption and we can only talk from going from 80 to 100 C.
On some engines higher temperatures actually improve the performance and I bought aftermarket higher thermostat for my Ford diesel.
Would the thermostat stuck open and keep the engine at 30-40 C that would show at the pump.
 

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Black on Black 1997 E420
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Discussion Starter #7
OP posted about higher temperatures, than normal. Those do not affect fuel consumption and we can only talk from going from 80 to 100 C.
On some engines higher temperatures actually improve
Why would Check Codes say that a new thermostat could improve fuel consumption, then? He's quite the authority on this forum along with others, you included.
 

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"IMPROVE" fuel consumption? ;)
You are quoting a conclusion without quoting the details. I have no idea what you are talking about and statistically the dog is buried in details.
 

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Black on Black 1997 E420
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Discussion Starter #9
My source was from within the M104/M119 Thermostat DIY sticky context, on page 2 comment #18:
Nice job, texholdem. Now you're immortal. :)

Good luck with chasing the mileage gremlins.

And based on the fact that your old one was stuck open, I'd bet you'll see a decent mileage improvement. Particularly if you're in a colder climate, then engine would take a long, long time to get to operating temperature, and if you were driving moderate roadway to low freeway speeds it would probably never really get to the proper temp. Surprised this didn't reflect on the dash gauge.

Take care and enjoy the ride,
Greg
 
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