Well all my driving is basically on the highway and still average 19-20 mpg, driving 5AT :/

 

Make sure your wheels turn free from the brakes, lots of times calipers get stuck and siezed up on the pins, dragging constantly.., pins need to be cleaned, boots replaced and then all lubed up with a good coating of silicone dielectric compound...
driving gently I can get 27 - 30 US MPG.
Leadfooting or hurry it's down to 18- 20!

 

whn i bought my 05 (44k mi) coupe in october i was consistently getting 360 mi to the tank, now Im getting no more than 250... I have put 16k mi on the car but the oil has been chaged every 3k with dino oil (was gonna go synthetic but was told it would increase my risk of OC issues). Only thing I can think of is tires?

What else would account for ~110 mi difference?

Car is a 6mt and although I do drive with a little "spirit" at times my tachometer rarely sees above 4K and I usually shift at 2k.

 

You must be joking? I always shift at 4k+ but when its time to rock'n roll, 6k+!

 

I hope your joking at shifting at 2k lol

 

I'll try this out but I think my brakes are good and free, just wished I knew exactly what coule be done...

 

i believe it!! I got 450-500 on a long trip. all interstate cruising at 80mph and a speeding ticket 80 on 65!! lol.. trooper must be bored!! lmao

But driving local city, stop and go... lol i average 12 mpg!!

07 coupe AT

 

It's hard to diagnose without actually working on the car, do you have a GPS/ Info cnter in your car...you can actually see what mileage you are getting...the sweet spot for optimum on mine is at 65mph..anything above it goes down and below mileage will drop too until you get into low speeds with cruise on..
Tell you what, get a paper and pen, highway cruising with cruise control on at 50, 60, 70 mph, write down the rpm...I'll compare it to mine and see if there's a difference.
Is your's an automatic? Possible the lock up torque converter isn't working keeping your engine at a few hundred rpm more than if it was in lockup.
Again though, lift the car and see how free the wheels turn or are the brakes dragging...even the parking brake may be dragging...always hated the drum parking brake on a disc brake system.
Interesting thing I've been trying, when slowly accelerating with the G the MPG meter in the info center shows it's just sucking fuel all the while it's taking you to accelerate, so for ***** and giggle I'll hammer it down to reach my desired speed then lock the cruise on, takes seconds instead of a slow steady acceleration...seems I get better mileage on the computer doing that!

 

No I don't have navigation man and tomorrow morning I'll take note of my rpms while cruising at those speeds. I'll try to lift the car on Saturday and see what I get as well
5AT btw

 

Alright well I noted the rpms and they are as followed:
50mph ~1900prm
60mph ~2300rpm
70mph~ 2500rpm

 

its going to be difficult to compare gas milage unless you live in the same area of the country. Different parts of the country have different temps, different slants and conditions of the road, so that will all effect mpg.

If you go to fueleconomy.gov in general the average for manuals combined is 23mpg and 20mpg for autos. Its just the benefits of a 6 speed versus 5 speed. Thats why newer cars come with 6-8 speed automatics.

Only real way to increase mpg is proper maintaince..IE new spark plugs, new air filter, change out transmission and diff fluid. Almost make sure your tires are at 36 psi, 40psi if you want a little more mpg.

 

Okay...you are over 200 rpm more than mine at all the speeds except for 70 mph..I'm wondering if your lock up torque isn't kicking in until the higher rpm. Might be a problem with the transmission module or the valve body of the transmission itself, I know on some of the autos I worked on there was a spring that lost it's tension due to heat and the lock up stopped working, but thats a whole different brand than Infiniti...
I also took a reading for mine at 80 mph too, 2900 rpm.
To see if your lock up is working, get it on the road after warm up, and get it to 50 or 60 and set the cruise. Cancel the cruise and let it wind down a few mph then hit it the resume...as soon as you feel it go into 5th watch the rpm's, should be a reading steady about 200- 300 rpm more than what you gave me, if it stays at that rpm you gave me and doesn't have a gradual drop after a few moments then the lock up isn't happening.
Hope this helps...it's a starting point for you.

 

damn alright man thanks for the input and i'll try your method out to see if it kicks in

 

I just filled my 2003 5AT. I got 300 miles on 16.842 gals = 17.8 MPG. That sucks.... I really don't drive it hard, only a little spirited once and awhile. It has been a little warm so I have had the air on a few times. It is completely stock with no mods yet, I have only had it just over a month now.

 

awd mpg blowsss