Update on lower temp thermostat (while I'm posting stuff.) Questions and theories inside.
01-18-2006, 11:32 AM
#1
AudiWorld Super User
Thread Starter
Update on lower temp thermostat (while I'm posting stuff.) Questions and theories inside.
I have been watching the oil temps lately, and they've really cooled off, which is great for those who want to track their cars. However, this has a trade-off that I had wondered about, and now I know. The gas mileage has dropped, significantly. I was getting 380-400 miles/tank, which is now closer to 300-320. That takes me from 25-26 mpg to around 20 mpg. Definitely not a good thing, especially with gas prices climbing again.
As for why it has dropped, I have a pretty good explanation theory. The car is shooting for a certain coolant temperature, and if it doesn't meet that temp, it has to expend more gasoline to create more engine heat in order to heat up the coolant. Ever wonder why diesels run with radiator covers in the winter? It's a similar theory.
Of course, if that's the case, does anyone have a way to reprogram the ECU to look for a different coolant temp, and would I need a different temp sensor?
I also wonder if this affected my hp numbers as well, and I run into a dilemma with that one. If my mileage is going down, then I'm obviously running rich. If that's the case, then why did the tail sniffer say I was running lean while running on the dyno? That's one that I've been pondering for a while. If anyone has input, please share it.
So, is the cooler thermostat worth it? That all depends. If you track the car a lot or exclusively, absolutely. It'll guarantee that your oil temps are lower. However, if you are a commuter, don't track the car, or if you live up north, it's not for you. I live in TN and the oil temp hasn't gotten but to about 190 after a 45 minute drive lately with our 30 degree temps, so I imagine it'd be even colder in MI, PA, NY, etc.
If you have any questions, let me know. I'll supply as much info as I can. Just called my mechanic to get me a cost to replace it with a regular one, btw.
To RyanS4, Hal_S4Shizzle: Now we know for sure.<ul><li><a href="https://forums.audiworld.com/s4/msgs/2220826.phtml">Link to original, more hopeful, post</a></li></ul>
As for why it has dropped, I have a pretty good explanation theory. The car is shooting for a certain coolant temperature, and if it doesn't meet that temp, it has to expend more gasoline to create more engine heat in order to heat up the coolant. Ever wonder why diesels run with radiator covers in the winter? It's a similar theory.
Of course, if that's the case, does anyone have a way to reprogram the ECU to look for a different coolant temp, and would I need a different temp sensor?
I also wonder if this affected my hp numbers as well, and I run into a dilemma with that one. If my mileage is going down, then I'm obviously running rich. If that's the case, then why did the tail sniffer say I was running lean while running on the dyno? That's one that I've been pondering for a while. If anyone has input, please share it.
So, is the cooler thermostat worth it? That all depends. If you track the car a lot or exclusively, absolutely. It'll guarantee that your oil temps are lower. However, if you are a commuter, don't track the car, or if you live up north, it's not for you. I live in TN and the oil temp hasn't gotten but to about 190 after a 45 minute drive lately with our 30 degree temps, so I imagine it'd be even colder in MI, PA, NY, etc.
If you have any questions, let me know. I'll supply as much info as I can. Just called my mechanic to get me a cost to replace it with a regular one, btw.
To RyanS4, Hal_S4Shizzle: Now we know for sure.<ul><li><a href="https://forums.audiworld.com/s4/msgs/2220826.phtml">Link to original, more hopeful, post</a></li></ul>
01-18-2006, 11:45 AM
#2
AudiWorld Super User
Wow! You get 26mpg in an S?
That's damn impressive. What's your average MPH?
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01-18-2006, 01:06 PM
#10
AudiWorld Super User
Damn...I also have a 40 mile one way commute, but best I can average is like 36MPH and 22mpg.
Damn traffic!