So far this has only happened once for me but what I did was, and I have an F-Sport so if you have a non F model I don't really know where it is, but you can turn on Eco mode without being in Eco mode. There's an option in the dash settings for an extra Eco mode (I call it "Eco+) where when in Eco or Normal (turning the round ****), it gives you the little Eco indicator on the left outside the LCD screen. When you have that on, you can drive in Eco in the city and then switch to Sport on the highway and it will increase your MPG (in my 250) to about 23-24 city to about 26-27 highway. The highest MPG I have gotten was 27 but so far only once. I have also been testing other things to get the most MPG out of my car.

 

My daily commute is about 42mi. My avg mpg at fill up is about 25-26mpg using the 'total mileage/gal filled'
I always drive in Sport+ and manual mode. You can manually row your gears to 8 instead of of 6-7 in auto mode.

Shifting under 2K RPM's help too!

Hope this helps!

 

I find it hard to believe to achieve this with IS350. Yours must be 250.

 

The Eco light in the dash is purely a display of your current driving habit, whether it's "Eco" or not "Eco. It doesn't put the car itself into a different mode. It corresponds directly to the Eco gauge in the display. The only way to get into Eco mode is to turn that big ole ****.

Here's a snippet from the manual.

 

I'm was getting 22mpg in my IS350 in the beginning. Now I'm averaging around 24mpg with split Freeway/City driving. More than a few WOT romps in Sport typically drop me into the 23 range. If he is traveling 42mi than he is most likely hitting open highway so 25-26 is definitely believable.

Trick is, we don't have the traffic that you big city drivers have. That's what destroys any type of fuel efficiency this car has.

 

i turned off that damn eco light in the settings, INCREDIBLY annoying

I took a trip to san antonio and got 26.3 in eco mode on my 350 driving about 75-80. Pure highway though

 

What I meant was with S/S+ mode.

 

no one said we can't turn off the traction control when dry and turn it back on when wet? =)

 

i go about half highway and half road.... gas is killing me... =(

 

If you refer to the 250 as a 350, then yes, I have a 250!