I filled up yesterday, and it used up about half of the tank in less than 150 miles. On the way home (about 40 mile ride), I went from 3/4 tank to a 1/2 tank, but I was speeding . This is an awesome machine - I haven't gotten a chance to race a real competitive car, yet. One of these days, I'll try to drive in cruise control, and see what my gas milage is (I have to admit, it'll be really difficult to "cruise" in my G ).

 

I have kept a track of my gas mileage since it's first tank of gas. I keep a company gas card so I just write down the mileage every time I fill up and check the statement at the end of the month for amount of gas.
The first tank of gas was good for about 18 mpg. It just kept going up... so at 1200 miles... I was getting 19 - 20 mpg. I regularly see 20+ now... 20 - 22 mpg. I don't baby it... but I don't floor it either. I do 60% freeway.
My old Acura TL did 23 - 24 mpg @ 75% fwy.
The gas mileage is decent for this type of car.
I think C&D got like 16mpg (or MtrTrnd). Of course they floor the car at every stop sign and stoplight. =)
If you think that is bad... my lil bro's honda will get 24mpg on it's best day. His civic ex did 26mpg regularly. I wouldn't give up 100hp for 2mpg... in $$ terms - +/- $2 per fillup.
Forget what the manufacturer says, and what the magazines say they saw. When it comes down to real world driving... we still have it good. Don't take my word for it... just check out how many times a week a mustang v8 has to stop at a gas station, and they still only make as much power as we do.

 

The real question is, how many gallons of gas can are car really hold. I'm consistant at 16-17 gallons. Not once I was able to go beyond that. Even when gas lights goes on for awhile. Hypothetically we should be able to at least squeeze 400 miles per tank driving all freeway. I guess it is time for me to take a Vegas trip to find out.

G35C 6MT / E55

 

OK, ok, eveyone's gonna call me a little old lady, but I've got about 850 miles on C6MT. Came from dealer with very full tank. Overall mileage on three fillups has been a little over 23.5 mpg. About 50/50 highway and city.

But I do skip shift, 1/3/5/6 (or 1/2/4/6) and I'm into 6th on suburban streets with distance between lights (and def on highway). Also, I'm babying it during break-in---below 70 mph, shift before 4K rpm.

So, that's it. By this Mon./Tues., I'll have break in done then we'll see if mileage stays up there when I'm normally cruising highways at 75-80 mph. I doubt it.

 

@ 4700 miles I have checked the gas mileage on every fill up, using premium only, I usually get 17 mpg 50/50 hwy, the best was an all hwy trip - 75 mph in cruise control - 21.5 mpg. This week with a little heaver foot and a little less hwy I got 14.1 mpg. The NAV trip computer always reads higher then the actual measured mpg. Coupe w/ 5AT.

5AT,Brilliant Silver, Premium Pkg, 18" Perf. Wheels, Aero, Nav.

 

If you want to get good mileage and you have NaV then play the gas mileage game like I do. If I monitor the fueleconomy while I drive I can get avg 31mpg on the highway and around 25 off the hwy. It's tedious though. when I dont pay attention I get average 19. My mileage went up with the switch to Synthetic too. No complaints here.