Hi my fellow infiniti owners I have a problem and I don't know what to do. I have 2004 infiniti i35 I bought the car 1 year ago the MPG was fine now I think to low it's 7.5 in the city on highway 15 16 mpg can anybody tell me what's the problem? I know I have to change the muffler but I don't think it has to do anything with mpg please help

 

How long has the low MPG been going on?

Have you noticed anything else -- lack of power, noise, wheels feeling hot after driving around?

 

is your Check Engine Light on ?

 

No loss of power nothing is happening it drives the same as the day I got it ohh wait I have this rattle when Rpms about 1800-1900 that's about it. No check engine light. What can it be and it's going on for 1 month

 

That rattle is probably in your exhaust somewhere, like a heat shield or something.

 

Mileage?

replace the following:
Spark plugs, 02 sensors (4), clean or change MAF sensor.

 

Just wanted to throw in that I have an '01 with equally ridiculous mileage. I read on this forum somewhere that people get 300 miles of range "when driving hard," when I try to drive as gently as possible, use premium gas, and barely get more than 200. I switched out one of the cats, but haven't done the O2 yet. I doubt that's costing me that much of a range loss, especially considering it's a huge tank...
Oh yea, I have 143k miles I think.

 

I get about 245 miles a tank total, when I replaced 02 sensors before and that didn't help. I also replaced spark plugs and that did not help at all. I am just curious how can someone get 300 miles a tank, especially driving hard, I was able to achieve same results only by driving on interstate about 70 miles per hour.

 

I don't remember where I saw it, but I'm pretty damn jealous. My '08 535i gives me better MPG/range than this does man (well, ignoring the age). About the same tank size, but that has 70+ horsepower more than our I30s.