Good luck, I'm sure the car just needs to break in properly. Also one thing I heard but never understood was braking too fast brings your mpg down.

And for the break-in period, it will be over soon enough, then you''l be ready to open the G up on the open road

A/C does bring down your MPG, but I have no idea how much. I would still use it, just put on the econ mode.

 

And yet I thought the gas tank held 20 gallons. 200 miles at 13mpg is only about 16 gallons.

 

most i've ever put in after driving 20 miles after the fuel light came on and the needle buried is 16.4 gallons.

 

Then the reserve is high on your car. When you claimed so many miles on a tank, I was taking it for a full tank.

 

Have 2008 G35x Sport. 2,1000 miles on it. Did not follow break-in procedure because dealer explicitly told me to ignore it, and just DRIVE THE CAR! Getting 19-20 mpg, about 60% highway at 75 mpg (no cruise control); only been using 91-93 octane fuel. When I can really get on it I do and accelerate aggressively - however suburban traffic is really hindering my G35 experience!! Grrrr!!

 

Wow! Just bought a 2008 G35X yesterday. What did I get myself into? I can't believe 9.8 mpg unless you're in very heavy traffic with constant accel / decel and a lot of time sitting at idle or you're driving around in the wrong gear (there are five to chose from). I've always experienced something pretty close to EPA estimates with all our cars so, I'm expecting the same with the G35.

If you're not in extreme traffic and you're not driving like an idiot, the air/fuel mixture would have to be extremely rich to produce those numbers. I would think that would create driveability problems that would be readily apparent.

Aside from the ECU fuel management, is the parking brake either set or not releasing properly? Again, I would think this would create problems that would be readily apparent.

Has the OP swapped out the ECU and fuel injection for a carbuerated setup from the 60's?
Hauling cement in the trunk?
Only driving uphill?
Towing a trailer?

 

All of above. hehhehe

tg