Doubt having ECT PWR on all the time will do anything bad to the tranny.

But as far as the MPG goes, there's too many variables that go into how much MPG your getting. Where you drive mostly (city/highway), temperatures, car service history, tire pressure and most importantly, the way you actually drive the car - all have an effect on the resulting MPG you get.

Some people get 12 mpg out of their IS350, others can get 30+, it all depends on a variety of factors.

 

i get 19... I think 19-22 is average for normal driving in the city for is350...

 

no matter how conservative I drive i never get more than 27 tank average.

 

It's not super common to get >30 highway in a 350... but 28-30 is very common. (and my window sticker said 20/28 when I bought my car in 2008 FWIW using the "old" mpg system...and that has seemed pretty accurate in my experience.... (it's more like 20-22/28-30 depending on conditions and driving and whatnot).

I've never gotten as low as 26 mpg for any all-highway tank of gas when I've taken roadtrips... 27.5 or so is about the worst I've gotten on such a trip and that was when the car only had a few hundred miles on it.

 

21 is the best I've seen on my car...

 

21-22 MPG with no ECT PWR.

 

I average 24 MPG.

Worst I've ever gotten: 13.66
Best I've ever gotten: 28.26

 

18mpg, all city, all flooring it, all the time

 

I have a semi-related question not worth starting a thread over: What are people seeing as the average drop in MPG in winter vs. summer driving for their IS350?

I understand that for a lot of reasons, your gas mileage in the winter will be worse than in the summer holding all else equal (http://www.metrompg.com/posts/winter-mpg.htm).

So what kind of drop are you seeing?

I ask because this past weekend I took a long 400 mile road trip or so all highway driving, and I got 25.6 MPG or so for the tank. This was almost 100% highway driving.

In warmer, summer weather, it wouldn't be unusual for me to get 30-32 MPG on the highway.

So is that drop for winter conditions in line with what others are seeing?

 

I get 22mpg on average 50/50 highway/city with ect normal

 

I usually get 18-19 MPG according to the on board MPG-meter, I've only had it for 34 days.

09' IS350 w/Factory 18"

Edit: oh and auto climate on all the time.

 

70% City/30% HWY with 32 psi in the tires. With my foot continually on the loud pedal I get in the 21mpg range.

 

I've only got 500+ miles on my 2012 IS350 AWD so I don't have a large sample size but it looks like I'll be getting around 20 mpg on average. But then again I have been "experimenting" with it a bit

I'm assuming that I'll take a hit for the AWD as well.

 

I only get 12mpg in my 06 350... 60/city 40/highway
its me not the car ... i got 30mpg on a 2 1/2 hr trip from Ny to Boston
I just like driving fast!

 

^ wow 12 mpg .. @_@