I maintain my car fairly well and average about 19-21 mpg city depending on how much I floor it. Some weeks are better than others. lol Having lightweight wheels helps with my works that weighed 30lbs each I noticed I'd only get about 300 miles per tank, now with my te37's, same size, I get 330-360. Much better.

 

I also doing a poor mileage, 12 MPG (85% city), i drive like a grand-ma most of the time
2004 G35 AUTO with 64k km, the car was never used during the winter, its is first winter now with me

I cleanup-ed my air filter last night and MAF, tomorow I will fill my tank with a injector cleanup in my tank, hopefully that will improve my mileage.

The way i drive I should get around 19-21 MPG not 12!

I also have a question, the previous owner of my G35 put a z-tube with K&N air filter, is the z-tube can decrease the mileage, I saw in this forum telling its improve?

I ordered a OBD2 Bluetooth device to connect on my car with my phone to see all the sensors and see what is going on, the check engine does not come on but I suspect a sensor have an issue but not enough to light up the check engine? Any tips to check with OBD2? Does errors can occur even if the check engine is not on?

 

Well, I used to work at a Volvo dealership and that by no means says I'm correct here but here are some things that you could check. Two of the main fuel controls on a car are ECT sensor and O2 sensor. Your 02 sensor could be lazy causing poor mileage. Aslo the ECT could be sending incorrect signal (voltage ) to the computer. However you should be able to smell excessive fuel because of this and it would be running crappy. Another big one on Volvo's is the thermostat. If the car never reaches operating temp or takes forever for the temp guage to move to where it normally is it will burn hella fuel. Of course if your due for tune up that will add 2-3 mpg

 

After 4 weeks of data here my result:

week 1, 95% city, got the car, I drive normally, I get 13MPG
week 2, 95% city, same thing, 13.7 MPG
week 3, 75% city, K&N filter cleanup, fuel injector cleanup, 14.3 MPG
week 4, 95% city, 13 MPG

Now I have done a ECU reset and hope that will do something, I will check OBD2 sensor this weekend but I have no check light, but maybe some sensor like O2 are defect or my ECU is always running in open loop.

 

Sub'd

 

Wow 12mpg thats bad! I get 19 mpg around town.I use only 93 octane gas though.what type of gas are you using?

 

Here we can get 91 (higher) or 89 (medium) or 87 (low)

I use 91 so far

 

Welcome to the Performance world where MPG are bad but the ride is always fun.

 

G35's are really only fuel efficient on the highway at 75MPH with the cruise control set, downhil with a tailwind after taking a dump.

Other than that, getting mileage in the teens is somewhat normal. My AWD is a heavy bastard, and i manage maybe 15-18MPG city driving only...even when trying to baby it.

Highway i can squeak out 24-26MPG, but only when cruising with the CC set. Minute i get off the highway, it drops like a rock.

I've run 89-93 octane with no difference in fuel economy really.

 

13 MPG vs 15 MPG is a lot, I drive like a grand-ma, so I should get 17-19 not 13...

 

If you do a lot of short drives (ie. less than 10 miles) 13 MPG for our cars isn't out of the question.

 

Alot of my driving around town is 6 miles.My car just gets warm and lm at the job.l l get 19 mpg .13mpg l would got to infiniti and have them find out why its so low mpg!Even if l drive spirited l get 17.5 mpg!

 

What are your driving habits? Where do you mostly drive? Around town?

 

I driver mainly to go to work and return back home, its around 15km x 2 per day. But it take at least between 30-45 min to achieve that. I dont push the gaz pedal hard, my previous car was an honda civic hybrid, so i know how to hypermiles to get the max of a car, but my g35 really dont care how I driver lol just push lot of gas for nothing

I hope my ECU reset will do something, I am still waiting for my bluetooth OBD2 device to arrive, once I get it I will able to take screenshot of all the sensors and post the image here

 

If it takes 45 min to drive 9 miles, that's your issue there. Just sitting in traffic idling will burn a LOT of gas.

A honda civic hybrid is not a good comparison because when idling, the engine shuts off.

I hate to say it and be "that guy", but if you bought your g35 for fuel economy, you bought the wrong car. It's just not very efficient. My previous v8 mustang GT actually got better fuel economy than my G35.