Ok i know these cars aren't the greatest on gas to begin with but its gotten a little out of hand lately. I hadn't actually checked in a while, but on my last fill up i reset my trip odometer and as of tonight I am currently sitting at a little more than 1/4 tank and i have only gone about 160 miles. Now I've owned both an 06 sedan and a 03 350z and easily gotten anywhere between 280-320 per fill up. Right now I'm looking at probably in the ball park of around 200 and I've had similar fuel problems with the car for a while. I can almost watch my fuel gauge lower while driving

I don't have any check engine lights, the car has roughly 180k miles as well. Not sure when the last time the plugs were changed so they are getting replaced within the next week and I have no way of checking the air/fuel ratio. I know there isn't a lot of info to work with here but any help will be appreciated.

 

In in the same boat. Mines at 160 and sitting on empty. I just switched to full synthetic, fresh diff fluid, fresh trams fluid, and new pcv valve. No change at all plugs are next hopefully that'll help a little

 

These cars have issues with the sending unit for the fuel gauge, mine does this too. Fill up and see how much fuel you've actually used, I bet it's less than you think. There's a fix on here if you look.

 

Mines not it's consistently 12-13 gallons to fill up. I can usually get close to 200 miles (15mpg average)

 

That sucks, you should get at least 18 untuned, I get about 22 since Uprev. Since you don't have any CEL's change the plugs, how many miles since they have been changed?

 

I have no idea...which is why they're next haha

 

I've already cleaned the level sending units, didnt really change a thing. like i said the spark plugs are getting changed soon and i will go from there. i hope my cats aren't clogged and need to be replaced or one of the 4 O2 sensors is going out

 

Can an O2 sensor that is still functioning (but might be on its way out) cause fuel consumption to increase?

 

It shouldn't, you would get a code for being out of range or pre heating failure. Also bad cats should throw a code before the fuel mixture would richen that much. What kind of driving do you do? Short trips in traffic will kill milage as I'm sure you already know, 15 or less might not be that uncommon if you're in traffic a lot.

 

I get 21-22 with my 04 X combo

 

What's your driving style?

100% highway...i'll do 25-26MPG easy.

City driving....16-18MPG...less if i feel like driving a bit spirited.

 

i wouldn't really call it 'city driving' so to speak. i mainly drive to and from the gym and work. the gym is about 2 minutes from my house as well as one of my two jobs. my main job is about 10-15 miles from my house and its a straight shot down 1 road which averages about 45 mph and i usually dont hit many stop lights.

when i had my 06 6spd sedan and my 03 track 350z i never got this bad of gas mileage, consistantly 280-300 miles to the tank.

 

My mileage recently went down and I found the left rear caliper to be seized. Mileage went right back up after replacing it.

This was at 75,000 miles on a 2004 sedan.