03 G35 sedan gas milage

[pearlS13]

Hey guys, lately I've been noticing that I've just barly been able to squeeze out 400KM/ tank on my g35 sedan and I know it could do better. I always use 91 octane every fill up. The car get driven 90% in the city.I'm at 120,000KM's and I havent yet changed the plugs ( I bought the car used so I dont know if they were changed before?). My question is, would old, worn out plugs contribute to poor milage? Also, where exactely is the fuel filter located and how hard is it to replace?

Thanks,Alex

[87ninefiveone]

Old plugs will absolutely contribute to poor gas mileage. If your only getting 250 miles out of a tank of gas during "normal" driving however you've got bigger problems than just spark plugs.

Does the car run normally? No hesitation or a loppy idle?

More importantly, if the car is driven in the city how long are the average trips? If your not giving the car time to warm up it will always be running rich during the warm up period which can lead to excessive gas comsumption as well.

[vq35de]

filters, tires, plugs, Oxygen sensor lots of things. clean your throttle body, check your idle (rpm, temperature, etc.)

[pearlS13]

The car runs perfectly fine, it idles perfectly smooth, no hesitation or anything of that nature. I had the throttle body/intake cleaned not too long ago, i watched as it was being done and wow did it smoke alot! The one thing i noticed after it was done was that my idle increased by about 100rpm. It idles at about 650-700rpm fully warm now, and before it used to be at arond 550ish rpm.

Im going to start with replacing the plugs and fuel filter and I'll go from there I guess.

[G_whizz]

No doubt it's mostly my fault because I practically hammer it everywhere I go, I'm lucky if I get 300km's on a full tank of 91 octane!I can't help it, I just feel the need to drive fast all the time. I guess I'll be able to gauge my mileage alot better when winter hits because I can't drive as fast.

[vq35de]

No fuel filter on the g35 it is integral with the suction of the fuel pump. maint. free. (another good reason to run good gas)

I have an 03 6MT and I routinely get 320 MILES to a full tank in the city and over 450 MILES on the highway.

[mkaresh]

All good things to check.

You can see what others' are getting on my site, which reports the results of a relatively sophisticated real-world fuel economy survey. Page for the G35:

http://www.truedelta.com/fuel_...est

Just a few responses so far, this is just getting started.