So i own a 2003 g35 5at, and it averages 186 miles to a tank of gas with mixed 40% highway and 60% city driving. I use 93 octane and the only mods on my car are K&N Intake, Borla exhaust, and helix test pipes, I also have a small leak where my header connects to my test pipe. I changed the oil like 300 miles ago, i am yet to do my spark plugs, but idk what is wrong with it. shouldnt i be getting towards 300 miles to a tank? Should i do the reset pedal thing? I knew this car had pretty bad mpg, but still thats just way to low its like 11mpg lol

 

With the mods you mentioned did you at any time remove the negative side of the battery while installing? If not, you should have! Remove it for about an hour, reinstall and drive your G normally. Another thing that might help, clean your intake sensor...has that ever been done? If you're considering a plug change you must have considerable mileage on your G, what I posted should help...
Gary

 

fluids have big effect on your mpg. When was the last time you changed gear oil? Transmission oil?
What grade of motor oil you using?

And just like Gary said. If you considering spark plug replacement, you must have some serious miles under your belt, so might wanna have a Throttle body and mass airflow sensor cleaned.

 

It has around 115k on it, I have yet to touch the trans oil or the gear oil. Nor have i cleaned the air sensor, how would i go about doing that?

 

http://infinitihelp.com/diy/gcoupe/

 

^ I learned alot from that site. It has HELPED!

 

Give thanks for all goodness.

 

I get 210 miles to a tank on mine mixed city/highway. Our cars are not fuel efficient at all.

 

Thanks!

 

Pure hilarity. There is a free thanks button to guys giving good info and idiots don't use it.

 

I get about 380-400 miles before the gas light even kicks on. You guys must drive like a maniac. I only have a few spirited spurts of driving per tank.

 

Holy ****!!

 

Other than doing some maintenance to help improve MPG, City driving absolutely murders MPG on our cars. Worst tank I have ever had was 215 miles and that was all driving around Miami.

mostly highway? No problem

 

Not surprised @ 400 miles on a tank, GA roads arent NYC,NJ, CT roads! I get 300 on a tank before the light comes on. 186 miles out of a tank is an effing horror story. Time for a full tune up.

 

Atlanta traffic is no joke either but I'm sure the NE can be worse. I drive about 60-70% highway with the rest city. It all comes down to how you drive and good maintenance.