Over 27 mpg on the last tank! My thermostat was stuck open, which means the engine wouldn't get very warm. The temp needle would barely climb above C in traffic, and it would stay right at C or even below on the highway. Others said it shouldn't cause any problems.

I had to drive to Charlotte before I could get it fixed. Rountrip on one tank, 414 miles. My gas mileage was just over 27 mpg, a new record for this car. I drove about 80 mph the whole time I was on the highway. About 100 of those miles were city miles.

Is there some strange explanation for why a cooler engine would get better mileage? Anybody else noticed this?

Yesterday I got the thermostat replaced. It will be interesting to see my mileage on my roadtrip next week.

 

thats excellent

 

Well with a fully functioning thermo, I've gotten up to 33/mpg and average 27mpg on the highway so... nothing special

 

This doesn't make any sense. If your car is running cold, it's more likely to run rich and use MORE fuel. With few exceptions, engines run more efficiently as their operating temperature increases. If you have ever studied thermodynamics (remember the Otto cycle?), you will know that an engine's efficiency increases with the difference in the reservior temperatures (the air and the combusting fuel). That's one of the reasons why Cold Air Intakes help, because the air is cooler (air density is also a plus). If it wasn't for the limitations of the strength and integrity of aluminum and steel at high temperatures, engines could run much hotter and get more power on less fuel.

27mpg isn't all that special for a 4th Gen. At 221,000 miles my car still gets 30+ mpg on the highway. Last year she set a personal record at 34.2mpg!

 

I fear this is going to turn into yet another d*ck measuring contest.

 

You're going to wear out your engine uber fast.

 

Put your rulers away kids, King Kong is here.

 

That was my first impression, too. But if there is more friction in the engine, that would heat up the oil, right? I've already replaced the thermostat, so that's not a long term issue now. I posted my query about running cold earlier in this forum.

I'm impressed by your mileage. This is my second 4th gen., and my city mileage is usually around 23 mpg, and my highway just over 25. I drive fast.

 

Don't they all?

 

what if the engine was actually at the right temp but the gauge just wasnt reading right because the thermo was messing up or something.
did you open the hood and check the temp manually?

 

I couldn't get much heat through the heater, which is consistent with the engine being overcooled because the thermostat was stuck open.

 

maybe it is a coolant temp sensor.......my thermo stat was stuck open and the car would warm up to regular temp....it would just take a really long time. i would just go and get it replaced.......

 

i live in Raleigh N.C. and made a run there befor and got about the same...

 

With my experience I don't think it really hurts an older car to run it with out the thermo, but newer cars with ecu's almost have to have them in order to achieve maximum power/mileage. I used to install 160 degree thermo's but I don't believe they make them for our cars?? Does anyone know? I've never replaced mine. Don't we have 180 degree thermos?