I think our problem is 300 horses get very thirsty if you don't run them at high speed (60 mph and up)over long distance. A trip from Virginia to Philly up I-95 will usually get me ~25-27 mpg. Normal local driving will eventually drag that down to 16-18 mpg, depending on mix of high speed driving included.

 

I had a huge drop in MPG the first year I owned the car. On my 4-5th oil change the service advisor asked me if I wanted the injector service done (mileage indicated) and being in the automotive field I thought this was complete crap but figured I'd have it done anyway. Jumped me 80 Miles per tank which was huge. Gave me an extra 2-3 days between fill ups and hasn't been a problem since. Nissan/Infiniti says that should be done roughly every 35K. Just a helpful tip. Not a huge expense, it was like an hour labor charge. Just something to think about.

 

As an addendum to my previous post, I took my '07 6MT Coupe on a run up to Michigan (MSU) from Virginia for a college alumni event last year, about 760 miles each way and mostly highway until I got to the campus. My mileage averaged about 27 mpg for the trip, speed limits were mostly 65 or 70 so I kept it close to that as much as possible. Once I got back home and mostly suburban sub-highway speed driving, the mileage gradually returned to the 16-18 mpg range over the next 2 weeks. I mostly follow the dealer recommended maintenance schedule, use standard 5W oil as posted on the oil filler cap, tire pressures as specified, etc. I think the conclusion to owning one of these beasts is - drive fast and drive far if you want good mileage.

 

+1

I too keep a spreadsheet and record every fill up. I did this for my recently traded in 06 G35 and started another spreadsheet for my G37S.

On my 2006 G35 I used 7170 gallons of regular 87 Octane over 171431 miles for an overall 23.908 miles from December 31st 2005 to August 31st 2012.
My best MPG on my 06 G35 on a tankful from South Carolina to Florida in May 2007 was 28.830 MPG. My G35 always got better MPG in 70 to 80 degree temperatures and I've already found this to be true with my G37S

This photo was taken in September 2012 just after taking delivery of my 2012 G37S. I filled up and drove 50 miles to work at 65MPH on cruise control



Now that the weather in NJ has gotten colder the same trip a few days ago had a mileage drop to 25.6 on the display. The temp in NJ has dropped from the mid 70's to the mid 30's in the early morning hours



This photo shows my MPG results over a two week period of dealing with hurricane Sandy with short trips, traffic, and gas lines



As you can see things are back to normal as is my MPG

I use OEM air, oil and cabin filters, as well as 5w-30 oil.

Keep your air filters clean
Photo taken after 10k miles on my 06G35



The air filters are much easier to change on my G37S



I did a one month test on my 06 G35 using premium 91 and another month using premium 93 in 2009. I seemed to get better mileage using regular and I've been using regular 87 octane ever since. In my opinion premium is a total waste of money.

My best MPG so far on my 2012 G37S was on a tank full of regular in September was 26.19 MPG going 315 miles and used 12.029 gallons to fill up

Telcoman

 

Anybody posting on Fuelly.com?

I have posted all fill-ups and it keeps a nice historical graph of all gas consumption and related stuff.

 

Would be nice if we can get are rpm down like the g37 when on the freeway

 

Stop shifting at 6k. Problem solved.

 

Anyone else get 12mpg keeping it under 3k at all times?

 

Not me. I get 20 now combine city/freeway

 

[QUOTE=telcoman;6630814I did a one month test on my 06 G35 using premium 91 and another month using premium 93 in 2009. I seemed to get better mileage using regular and I've been using regular 87 octane ever since. In my opinion premium is a total waste of money.[/QUOTE]

I agree. I run 89 octane in my car which i do 90% highway driving with about 25K miles per year.

I did some back to back monthlong tests using both 93 octane and 89 octane and noticed no difference in fuel economy. I now run 89 octane

 

I put 87 in both my cars and I still get about 300 to the tank

 

Can anyone else confirm this? There has to be some way that if filters fuel before it sends it to the fuel rails.....

 

There is a fuel filter in the gas tank. There is no maintainence interval for it, but several members have replaced it anyway.

As for the injector issue, it's plausible, but I would think it would trigger an CEL at some point when the computer notices an imbalance in fuel usage for each bank of cylinders. It could happen though, but recent experience with a different car showed me that a dead injector did trigger a CEL for me. Lightly clogged? Who knows.

 

I traded in my 06 G35 with 171796 miles. Never touched the fuel filter
Still ran like new. Plugs were changed at 106682 miles



Telcoman

 

Mine seems to get 20-21mpg no matter how hard or easy I drive it. It's the only car I've had that acted that way. I wonder if the injector service might help. Is that just a bottle of additive they add to the tank or something?