hello i have a black on black 2003 g35 coupe 6 speed,

i just bought this around a month ago ,

here is my issue .

i put a motordyne plenum spacer on it ,
stillen z tube
e3 spark plugs

did a tune up on the brakes
and oil change with synthetic
did the valve covers due to leaking
at this time i replaced pcv and cleaned the mass airflow


but i am getting the worst gas mileage ever

from right full to 1/4 tank it is 44km..

and from full to 3/4 im at 276.km

i am thinking it may be the plugs that are doing this.

was thinking about reprogramming the throttle body,

i live in wasaga beach just use it for short trips does not sit at idle for long periods of time..

what does everyone think i dont drive it to hard.. should i change the plugs to a ngk iridium or a platinum to see if it gets better

 

sorry if im reading this incorrectly, but did you just basically type out from full to 1/4 u get 44km but from full to 3/4 you get 276km?

 

Yeah lil confused???

 

You need to properly calculate your mileage before we can make any useful recommendations. Here's how, fill it up, reset the trip odometer, drive until the light comes on, refill the tank, then divide the miles driven by the gallons used to fill to get the MPG. I usually get around 21-22mpgs but the gas gauge doesn't accurately reflect that. After a half tank I'm usually around 150-170 miles but by the time the light comes on I've driven about 350-370. Get an accurate measure of your mpg then we should be able to help you out. If you're really concerned start by changing your oil, filter, air filter and use a good fuel injector cleaner (Chevron Techron) that may help.

 

i get around 16mpg if i do 100% city (240 miles when the light comes on). so if you're getting 171 miles when 3/4 of your tank has burned off, the ratio about seems right. what mileage are you at? fuel injector shouldn't be necessary.

 

Your gas mileage will improve if you stop listening to your exhaust when you drive, turn up the tunes. When you own a cool ride like ours it's almost impossible to get great mileage unless you're on the road and use your cruise control and don't play, "I can get there first!"
Gary

 

Those e3 spark plugs are not all that great.

Right now I have the stock ones in, but have a set of Denso's on the shelf waiting to be put in.

As far as your gas mileage goes, I agree with the posts above. Try what johnnyd6404 said to do. Then we can help you out.

I just checked mine and pulled 400 miles out of the tank. I do alot of freeway driving to work though. (And yes I do have a pic)

 

I agree also, but I can tell you that those E3 sparkplugs are some of your problem, specially if they are a different heat range "hotter plug'' from the factory plugs. The hotter the plug the more fuel you will burn.

 

sorry for the late reply, so my car is now away for the winter i was told resetting the ecu will help allot. to disconnect the batt for 8 hours,

but i would like to let every one know my gas mileage got allot better after getting rid of the e3 spark plugs, i used them for 3 weeks. i do not recommend them at all.

thanks for your help every one