So my dash tells me i can get about 300 miles on a full tank... when i get down to about 260 it says 30mi.

I used to push it to 325mi which is about 17Gal at about 19mpg.

I know the G has a 20gal tank is its about 380 mi at 19mpg.

so this last fill up, i pushed 375 at 21.1mpg (hwy driving)
i filled up about 18gals.

when i turned the car on it said 290 miles, i was hoping it would start working normally and not give me the warning light only 14gal.

just this morning, i was driving to work and the warning light came on. it said i had 58 miles.... and i am only at 240mi on a tank..

anyone else getting the same thing? i know i have more gas then the car thinks ill fill up at 350mi instead of 290mi.

 

I'm averaging 22.1mpg after 25,000 miles with 60/40 highway/city mix. I usually get about 400 miles to a tank full, fill up between 380-390mi just to be safe. I drive it pretty hard and fast about 50% of the time.

But if you're averaging 21.1mpg you should get at least 380mi to a tank full?

 

I do, but i am wondering y my car doesnt know that, and keep telling me to fill up 100mi before i really need to

 

I typically fill up at about 175 miles. That's at about 3/4 and I put in just under 14 gallons.

 

On your mpg that you state is this a calculated number or one shown on the dash?

I have an external trip meter that is OBD based. One of its functions is mpg. The other is miles to empty. The mpg is always off compared to the dash reading but is always within 1 mpg as well. I can make it very close by calibrating it.

I am not entirely sure how the number is calculated on the 'G' but a key point on the other OBD one is an accurate reading of the gallons per hour which is calibrated after a fillup and an accurate reading of the miles. You could do the same estimating off of tank level. This is the point. I think the 'G' has two level sensors and the tank is a stepped tank. If the miles to empty is estimated by tank level it is possible one of these is giving a false reading which in turn would give a false miles to empty reading.

You may want to keep track of how many gallons it takes to fill based on current level. Assuming you put in 20 gallons when empty (not sure if you can actually run it dry) if the reading was at 1/4 then you should put it 15 gallons, 1/2 you should put in 10, 3/4 - 5 gallons, etc. This may tell you where the error occurs.

 

Wow, well you guys are lucky compared to me. MY g calculates 13 MPG. This seems really ****ty. anyone know why this is? could it be that something is wrong with my engine that is making it eat up gas?

 

Did you calculate you mpg manually?

 

Guess I am not the only one. This happens with me as well, I mean I do drive a little bit well let's say spirited sometimes but most of the time I drive it like a nice luxury car. I find it hard to believe I average about 15mpg or so says my gauge. I have personally not yet tested it manually and not sure of the best way to go about it but I need figure out my correct numbers. I see you guys averaging much higher numbers and it just diddn't seem right.

 

i average on NYC driving about 250-280 for a full tank. 50/50 of both driving.
And the most ive ever filled up with my gas light on, saying i had 0.8 miles was 16.6 gallons.

 

If you mainly drive your G in the city you'll rarely get over 20mpg. Our 07 G got about 27 avg on the hwy (and this IS what our dash meter read as well). In stop & go city driving the dash meter usually avg'd from 16-20.

Our new 09 G37 gets about 2-3 MPG better on the hwy, haven't really checked how it does in the city though.

That's the price we all pay for those 306 to 330 ponies (and it's worth every penny!!!)

 

I've got an 07 G35 and try to push my tank as far as possible every time. I usually get at least 375/tank and 400 if I'm good . Not sure why yours is acting up but I think you should get well over 300 everytime even if you drive it really hard

 

I've been keeping a record since I bought my '07 G35 back in April.

I can tell you that overall, I've driven 3,307 miles at my last fill up and had averaged 16.3 mpg over that distance. On a normal week though when it's primarily driving to and from work, I average about 13.8 mpg.

I've only had three tanks/fillups where I've averaged over 20mpg.

I'm 90% sure there's nothing wrong, except the extreme stop & go traffic seen in my commute. Actually, I had a 2000 Contour SVT when I first moved here and one of the reasons I was okay getting rid of it was that I thought it was dying. It went from about 22 mpg no matter how I drove it, to 15 or so when I started working. I came to find out that it's not the car, it's the commute, it's a gas-eater.

 

how many miles are on it? maybe your fuel system needs to be cleaned! And i'm sure your tires are always what they should be? Your not carrying 600lb of gold in the trunk are you?

Rutland- have you tried re-setting your ECU?

 

from what I can tell, my mpg seems pretty normal for heavy stop & go city driving.

what's resetting the ECU going to do or better yet, what's it going to cost?

 

well your mpg seems normal like you thought, but you said the gas light comes on after 14 gal and i was just suggesting something like reseting the computer the simple way by disconnecting the ground battery terminal and re-connecting then let it idle or a few mintues. unless u've tried it.