I got an 06 g35x back in August and have noticed that my fuel economy seems to ran from only about 13-15 mpg on each tank. The car only has a little over 3k miles on it and has not yet had the first oil change, but how long until I see the fuel economy improve? I make sure to never drive hard on the gas or brakes and try to check my tire pressure every week or 2. Is this normal or should I be concerned?

 

Not enough information here.

If you predominately drive highway, something is wrong (unless you average 100mph).

If all city driving, what is the average driving distance and traffic like? If average 1 mile, for instance, most cars won't do too well, since it never warms up. Or do you wait long at stop lights due to traffic?

My 04AT averages around 16 mpg in city driving over the last 31K miles.

 

Mine has been slightly higher than that but only after I changed the oil for the first time. (city driving as well) You really should change the oil by 3k miles on that new motor. I replaced mine at 1k because most of the initial wearing is going be done by 500 miles or so. The motor is still breaking in at 3k miles but the majority of the wear was done in the first couple of weeks.
I would have that done shortly with some 5w-30 and see if it improves. Are you using high test gas, either 91 or 93 depending on your area? I would also suggest bumping the pressure up 2-3 psi cold, I felt like it sharpened the steering and will only aid in extending gas mileage.

 

I recently started posting raw data from my site's fuel economy survey. Page for the G35 here:

Infiniti G35 fuel economy

Not many results for the G35 yet, but most panel members don't know I'm posting results yet. I'll let them know in the update near the end of the month, at which point more will probably submit information.

 

I just got my 06 x the other day, I did my first road trip yesterday, 537 miles total. Speed was averaged @ 82mph (3100-3200 RPM) across northern New England, regular unleaded and averaged 22 1/2 mpg. Calculation were done theold fashion way. Total mileage on car is now 750ish. I think IfI slow down to 76 and the engine is broken in I will get around the 24 mpg on the window sticker. A little better than I thought! Whata great highway car!! Can't wait to drive in nasty New England weather and put the AWD tothe test, will it match up to my Audi's or Subaru's in the snow? I will letyou know!

 

Still have not broken 20mpg on my X yet, and I hardly ever exceed 85mph. Still better than any other 4X4 I have ever owned (several).

 

I've heard of low FE reseults for X's, you may want to ask the dealer to make sure everything is ok under the hood... i know some members tried new fuel pumps.

 

My 5AT '06 isn't an X but I get about 25-28 Highway mileage (65-75 mph on an occasional 250 mile round trip).

 

Average mpg per fill up is around 17-18 on super. I would say 70-30 as for city - highway. On long drives it bumps up to about 23 with an average speed of 80. Currently 23K

 

definately weird, i've never gotten mpg that low. i usually do about 50% city 50% highway.

maybe 100% city in the cold could do it tho ...