Well, I just filled my new 05 G35X up for the first time and I heard these horror stories of poor gas mileage with the G. I am just breaking it in and I only have 333 km on the car. After my first fill-up it worked out to 12.048 L/100km (23mpg). For a brand new engine I am pleased, cause it will get much better once it is broken in and I think it is off to a good start.
Wayne

 

Yeh, economy definitely isn't our G's forte, but it makes up for it in fun points.
Like you, I got mid 20's on both my G's when new and breaking in, and this will improve as you say as the engine breaks in.

With care , and at the speed limit, you can knock off 32-33mpg's on the hwy. That's no fun but it can get the mpg's if you give her a chance.

Enjoy the ride, and welcome once again.

Colin (GSM)

 

Here is my $.02 worth. The G is no fuel miser but it makes up for it with the fun and the power factor. Mine seems to run about 21-24 mpg in mixed driving and has not really improved with break in. The funny thing is I got 27 mpg on my first tank. I generally try to run it pretty easy, shortshifting and skipshifting frequently. I have only had a couple of good highway runs and on the first I did 28 and the other 31 mpg driving at about 115-120. I'm sure another 2-3 are possible with speed limit driving on the highway.