Long story short, I have a 07 35x tech 1100 miles. I get 14.8mpg. I was not driving hard, I was still breaking the car in. Also, When I have a cold start, 50 % of the time it revs and holds 2000rpms for a min or two. I even ad trouble shiffting in reverse. WTF!!!! Only mod that I have is a stillen exhaust, dealer installed. Any help? Any one with the same problem?

 

I'm probably averaging 14 or so (of course, I DO drive fast); your mileage should get better after break in. And yes, high rpm at cold start is normal, mine drops about 100 rpm every ten seconds.

 

High RPM's happen in every car I've ever owned or driven in, you never noticed this? engines always start high and depending on temperature will drop anywhere from 30 seconds to 3 minutes. you can just throw it in drive and tear off, but I'd recommend waiting a little bit to let the engine warm up and RPM's settle.

MPG for me is 20+, I have 4500mi so far. it was a little worse during breakin, like 16-18. as the car breaks in I expect to get another 2 MPG and average 22 for my 70/30 hwy/local driving. If you are getting 14.8 then you are driving the car hard, you might not be floring it or going into high RPM's... but you are unecessarily heavy on the gas. do you find yourself always at the front of the pack, or catching up to the next group? the car is fast, you are probably accelerating a lot faster then you think. compare yourself to the cars around you.

Also you need to learn throttle, when you get to desired speed, let off the throttle to where the car maintains it's speed. this is probably where you keep it. I've found that even at this point, you can back off the gas a good portion more and still maintain speed but use less gas. you'll see hwy go up to 30MPG while still mainting on flat surface. when at speed, back off until the car starts to loose speed, then apply just enough to maintain. it is a big difference.

 

High rpms at startup seem to be the norm for these cars.
Gets the cats up to temp quicker.. but seems to be excessive compared to other cars I own.
As for mileage... I have 2400 miles on my G35S now. I am averaging 22 mpg mostly city but some hwy driving. I get on it every now and then... but thats mostly normal driving.
It should improve as things loosen up some.. you do have a bit more weight and friction losses being an "X". Hang in there... it should improve.

 

The manual does say that it will rev high if the engine is cold, and recommends to warm up the car until it goes back down. My car does rev high, I believe around 2K RPM, and then settles down to about 1K RPM.

My mileage was around 15 or 16 MPG when I first got it, and has gotten better since. I got 24MPG mostly highway driving, last time I did the math. This is without using cruise control in the highway. From experience with previous cars, using cruise control helps improve gas mileage signficantly (but may depend on your driving style), since it accelerates/decelerates more gradually. The 24MPG I calculated was with the winter fuel mix, which isn't as fuel efficient.

 

my X revs high during startup too. and along that I also typically see my mpg screen drop about 0.2 by the time it revs down. I'm also getting pretty bad mileage at 14-16 with about 4000 miles.

 

My mileage is nothing to write home about either...at 7200km, doing around 15mpg? OUCH.

 

Put it in first and then reverse. This does help a little getting it into reverse. It used to be almost the only way to get Honda's and Acura's to go into reverse.

 

the unusually high cold idle is typical of cars that use push button starts and electronically-controlled starter solenoids, in my experience. it's a little disconcerting... i think it is an attempt to light off the pre-cats sooner.

 

Mine does this also,, I hate it revs so high on a COLD start,, heck when it gets to 0* or colder and revs like that with very cold SLOW oil going up to the top of the motor i am worried allready this car is by far the highest cold revver i have ever had.... btw, my mileage is around 19-20 65% highway to 35% around town,, with 1800 miles....

 

this is in fact another reason why i am switching to synthetic oil right away.

 

i get no more then 16-18 mpg on 50/50 city/highway driving.

for those getting 20+ they are bull****ing.... no way in hell. my navi should be accurate, and i get no more then 17 avg.

i never rev pass 4.5k.

i spending at least 200-250 a month on gas. compared to my integra. 65-90bucks a month.

you guys should have a cc strictly for gas. it will tell you how much you spend on avg..

even though my integra is turbo'd and can smoke my G, it still gets better gas mileage. wtf is up with that.

 

that is my case also... i had an integra gs-r and bought a g35... what a difference in performance... but what a difference in guzzling gas...

 

No BS - first tank of gas, which included the test drive, went 288 mi. on 14.4 gal - exactly 20 mpg. Figured it was a fluke. Got 20 mpg on 2nd tank too. Working on 3rd tank now. Had 45 mi. on car when I bought it. Do 16 mi. each way to work. No freeway, maybe 60% cruisin and about 40% at 30-45 mph, with traffic lights. No hard pushing, but get 4000-5000+ rpm time to time and mix it up with easier driving for break-in purposes.

 

most cars run rich on cold starts