I got that on the highway with my 2000 Trans-Am 6-Speed as well. My revs were even lower though, 6th was a .5:1 ratio!
It didn't like cheap gas though! Also, if you put the same engine in a car the weighs less and has a better drag coefficient the results are astounding. It's not uncommon for guys that swap the LS1 into an FD body RX-7 to see 33MPG on the highway, and be able to shame LS1 Vettes at the light!

 

I get about 380 miles per tank G35x 06

 

I have been averaging 18-20 over the past year mostly in town daily stuff... pushing it when able . I've seen 23 OTR.. never anything CLOSE to 30 mpg's like someone else had mentioned... unless you drive like 50 all day long!?!

 

I think best i've ever done instantanously was 25MPG according to my NAV, which isn't accurate anyway. To do this i got up to cruising speed, hit cruise control and reset it. I drove for a few miles like that and it was around 24-25MPG at a cruise. Minute i started using the gas pedal it dropped like a rock.

 

The best I got was 26 MPG on the interstate, no A/C, very careful acceleration, a small amount of drafting, and 65-70MPH. But that was before I knew about the 4% discrepancy in the odometer, so I guess that would be more like 27 MPG

 

I do greatly appreciate everyones input here. It truly helps so thank you.

The car has 47,000 miles on it. I just bought it from an Inifiniti Dealership. They said they did all the maintenance on it previously. This last fill up was the same mileage. 14. I tried different gas stations, didnt make a difference. I have tried different grades of gas, did not make a difference. I also do not have a AWD. I do run the heater a lot (because its cold lol)

I plan on taking all the advice here and calling the dealership. Since I still have a 2,000 mile warranty.

I have to say I'm really jealous at those of you getting more than 300 miles a tank!

 

When you run the heat, do you turn the A/C off as well, or leave it on?

 

I leave it on. I was reading some threads about that. It always stays on. Does that make a difference? Is there a way to turn it off?

 

^Just press the A/C button, if the little led goes off, the compressor is off.

 

yeah, this has been talked about numerous times. there's plenty of guys (including myself) who have achieved 30mpg+ in the G. my instance was on a road trip a couple of years ago, through Banff & the East Kootenays in AB/BC (Canada). i travelled 755kms (470mi) without the gas light coming on when i fueled up in Kelowna. i can't remember how much gas i put in (i posted this info in the past) since it's been over 2 years, but i was impressed. 95% highway driving at 100-120kmh (60-75mph)...

 

2004 G35x, heavy right foot.

Worst = 14.23mpg
Best = 21.36mpg
2 years average = 16.41mpg

 

Yup. prob a 1/2 - 1 MPG difference maybe.

Just push the button that says A/C until the yellow LED goes out. The word "A/C" should disappear from the dash display as well.

Unless it's hot out, or i need my windows defogged, i leave my A/C off all the time. And when i do use it, I make sure it's in "ECON" mode unless it's really hot out

 

We have the same situation. I bought my 05 G35 6 months ago from the Parkway Infiniti. The price was a little high though: 17,400. Their initial price was 18990. The car was in neat condition. It had 42,000 miles on the odometer. I have averaged 15-17 combined gas mileage which isn't good at all. I thought I could have something like 20 mpg combined. I mean having a freeway gas mileage of less than 20 mpg for any car less than 8 cylinders and smaller than a full-size luxury is kind of retarded at this age. I love the G though. It's a classic.

I have just cleaned the injectors (for $140 )and increased the tire pressures to 35 psi. So I'm going to see whether I can see a distinct improvement in that respect.

 

So I finally went to the dealer and it looks like they said I have a problem with the mass air flow filter? So it looks like my crappy gas mileage, was due to that! They are fixing it today. I am really excited to see what kind of gas mileage I will be getting after this.

I do want to thank everyone for all your reply and responses. I really appreciate the help, tips, and input.

Thank you

 

Mass air-flow Sensor, or High air-flow filter????
Or do you have a high air-flow filter that's messing with the air-flow sensor? (friend of mine had that problem on his F150 once)