One thing ive noticed with the G35 coupe(mine is 2004 with 82k miles) is that there is a great variance when it come to fuel efficiency. Myself along with many others are in the lower teens, some even lower in terms of mpg and ive heard and know personally other people get high teens(even 20) in city driving. what can cause such a disparity?

Personally i take very good care of my vehicle. I drive it gently, change oil on time, spark plugs, air filter, radiator fluid, everything is always in check. i dont understand why my G gets me only about11-12 mpg in city driving and 15-16 mpg hwy. that is pitiful. if it was a ferrari or V12 Benz id understand that gas mileage but on a 3.5 V6 that is unacceptable. pretty much i am wondering if u guys have any recommendations. i would really appreciate it. i took it to infiniti dealer and they said that "everything is fine." ive also been to local shops and they say everything is ok too. obviously something has to be wrong because this car should not be getting such pitiful gas mileage. is there some sort of emissions or performance specialist i should look for? i love this car and would hate to have to part with it because of this. also wanted to mention the way i measure my mpg: fill up and reset miles, come back for next fill up and jot down mileage. divide mileage by gallons it took to fill up. do it all over again. i have read on here about the ecu reset but that did me no good. thanks for hearing me out!

 

o2 sensors could be bad

 

I divide by 20 since that's how big our tanks are supposed to be, but I guess it would be wiser to divide by the amount that you put in since you're likely to fill it up again at that same point. The last time I checked I got about 19MPG with roughly 40% city/60% hwy and I drive at about 65-70mph on the freeway as well which should make things worse.

Driving habits as well as the area you live can affect your gas mileage. Do you drive uphill a lot? How high do you usually rev during normal driving? I noticed that you did mention that you drive it gently so I'll assume you're not stepping on the pedal more than halfway or so. Are you using premium fuel?

 

Thanks for the response guys. I live in Miami so no hills here. lol. in term of driving habits i am very conservative with it. shift b/w 2.5 and 3k rpm. this is a car i had wanted for a long time but the last 2 years have been a nightmare in terms of gas mileage. i already have it paid off and would hate to see it go. if i was to let it go i dont think i would ever get an infiniti again for fear of having this happen again. i really wish i could get to the bottom of this and know that indeed something is wrong, get it fixed and keep this car for a few more years at least. i had a couple of mechanics check my 02 sensors and said they are running good. i do use premium fuel and have tried mid in the past as well but no difference in mpg/

 

I got 24mpg avg between city and highway, before going FI. Now with bigger injectors and fuel pump I still get over 20mpg. Here's my questions:

How many miles do you get? How many gallons at that point?
Fuel octane?
Have you used sea foam?
Are you a lead foot?

Shifting around 2.2k rpms is usually what gets me over 26mpg hwy. If you follow all this then I'd say the next step is Osiris dyno tune.

 

Going by what others have said so far. It seems like youre doing something wrong. Not the car.

 

JNinja, I have not tried sea foam. I've been thinking about it though. I will look into the Osiris dyno tune. I am far from a lead foot. My car is automatic and usually shifts at about 2.5k rpm. Use 93 octane.

 

If your auto if shifting at 2.5K, that is a bit too much gas. Should be shifting at like 2K to be getting anywhere near EPA advertised numbers.

BTW, also try an ECU reset (you'll need to reset your throttle body and idle as well, but it's easy - there are plenty of DIYs).

Lastly, you are driving in a hotter climate being in Miami. This affects things as your car makes less power at a given throttle, making you apply more throttle and thus using more gas.

 

If you have a N/A coupe or sedan that's not throwing error codes you should easily be getting 300+ miles per tank. If you're not it not the cars fault, it's how you drive! We love to hear the sweet sound of our exhaust systems so you take it a little higher in the RPM range so you can hear it better, this is fun....not good for gas mileage.
Gary

 

Again I'm not a free spirited driver. Most of my shift are under 2.5 k rpm and rarely 3k. If i was driving with lead foot I wldnt even be posting here. Its just concerning that a v6 is wasting as much gas as some v10 and v12's.

 

Living in a place that's warm should help increase his fuel economy over someone living in a cooler environment..... all other things considered equal (referring to driving habits mainly, but also vehicle condition and also elevation). Warmer air means the car doesn't have to use as much fuel to attain the desired air-to-fuel ratio.... plus the vehicle's fluids will already be relatively warmed up in the morning, rather than having to spin molasses-like motor, tranny and differential fluids that drivers in the more northern states have to during the beginning of drives in the cold winter months. Use of the Air Conditioner will contribute to a decrease in fuel economy though, so I'm sure you probably use the A/C all the time given your climate. Even if you don't have the A/C on, but if you constantly drive with your front window defogger on... that will use the air Conditioner as well because it does this to dehumidify the air before it pumps it onto the front windshield.

I can't vouch for what the Auto G35's get for fuel economy because mine is 6MT, but I'm one of the guys who fits into the 22-24 MPG club for the most part. I don't drive my car in the winter though once the first snow comes out, so it primarily sees sunny weather when the temps are between 25 to 95 degrees F.

To the OP.... how long are your trips generally? Lots of short trips = less fuel economy because the car uses more fuel while warming up than it does after it's fully heated. What are you using for tires/rims? Oversized rims and tires tend to weigh more and take more energy to spin, resulting in fuel economy losses. Certain tires will also result in better fuel economy than other tires of the same size. There's also the possibility that your cats are partially plugged which would add a significant amount of back pressure to the exhaust and reduce your power and fuel economy.

Can you tell us what (if any) modifications your car has?

 

Hi, maybe this would help. I to live down here in south florida (Hialeah) and just got my 04 g, terrible on gas and everyone said put 93 gas. Well guess what I put 89 and have increased gas mileage and the car run no different. Hope this helps.

 

^^wth....how?

 

Lol

 

I boughmy 04 G in 2008. I haven't done any mods and it looks like prev owner didnt either. I have stock rims with recommended tire size. I think I'm leaning towards trying the seafoam as I'm running out of hope with thos car. Oh and my trip to work is 20 miles roundtrip. On long trips I still get shitty gas mileage. Think I might have to get an accord of thos doesn't workout. Will miss the G but not the unnecessary fuel consumption.


In regards to sublime's comment I tired regular too but no difference. What kinda mileage do u get?