Just did a trip from Jacksonville to Atlanta and back. Got 24 mpg highway at 70-90mph (400 miles using 16.67 gal at the fill up I did today). I get around 18 mpg City. I use BP Amoco 93 octane only. My G Coupe 6MT has 2400 miles. I think you should take your G in to get it looked at- 11 mpg is ridiculous. Are you sure you are calculating your MPG correctly? Are your tires properly inflated (too low of air pressure reduces your MPG)? Lowering the octane will make the MPG worse, not raise it. I wouldn't buy a used G or similar car if I knew the previous owner consistently used less than premium fuel. The sticker on the inside of the fuel door is there for a reason.

 

Are you sure you arent running the defog or air conditioner on? Remember that when you use auto econ that the a/c comes on too and that can reduce gas mileage. Just another idea to throw out to you.

 

Yes, but the low fuel warning light comes on at about the 3 gallons left point. I've gone well beyond that many times. The most fuel I've ever put in was about 18.8. I heard about someone who ran it dry (possibly here) and did in fact put 20 in.

The warning light and gauge are calibrated very "pessimistically" (as in most cars) so you can't blame them for not giving you enough warning if you run out.

 

i know that i put in 93 octane and i get about an average of 260- 275mpt miles per tank... i dont know how many gals in our tanks so someone do the math

 

I get about 17-19! Damnit I should drive freeway more

 

I get a little over 14 mpg in mostly city driving on my 2005 AT. I just reached 1200 miles yesterday(at last!), so for the most part have not been very aggressive while trying to stay below 4000 RPM.

 

This doesn't sound right. Do you have data to back this up?

The reason I ask, is because if I understand things correctly, the only thing the octane number represents is the fuel's resistance (or lack thereof) to detonation. With that said, if I understand how the typical modern electronic fuel injection systems work, the computer will advance timing and decrease the the fuel injector pulse width (i.e. leans it out) until minor knock is detected, and then backs both values off. Wouldn't this then *increase* gas mileage for a higher octane?

Of course, I am also assuming that the average ECU only adjusts these numbers in very small increments, and within a very specific envelope of values defined by the fuel map set at the factory, so it would probably take a couple of tanks to see a difference in one direction or the other.

Either way, ebuy929 it sounds like you may have problems. My recommendation to you would be to:

- Reset your ECU following the procedure defined by the service manual. I'm sure there is a posting on here somewhere that describes the procedure. Other then that, maybe someone who owns a service manual can post the procedure

- Ensure that your tires are properly inflated...check them daily.

- Keep very precise records for the next 2 or 3 tanks of gas (mileage and fuel down to the tenths)

- Use only 93 octane during your recording period

- Constantly make sure that your AC is off, and that includes the use of the windshield defroster.

If you really do have a problem, then most likely none of these things will help, and on that 3rd tank you'll still be getting 11 mpg, but at least you will have specific records (keep your gas receipts!) to show the dealership. I would use the 'A' trip odometer for tank to tank mileage records, and the 'B' odometer for total...so be sure to reset it when you start your records, and don't reset it again until after the dealership has looked at it.

HTH,
M

 

You are correct....lowering the octane would make your gas mileage worse, not better, all else being equal.

 

just picked up an 03 and I get 20.9...

 

hehe i dint mean direct my post @ anyone, but all in all, 11 mpg is still unbelievably low. i mean you get like 5-10+/- mpg if ur on a track redlining all the time

 

I read through the forum and I have to say that my gas mileage is on the low to bad side of what most people are reporting. I have an 04.5 coupe with 8k miles on it. On average I get about 12-14 mpg. I drive mostly in the city and I do drive it hard at times. I use 93 octane too.

Has anyone had the ECU reprogrammed at the dealer to address this issue?

 

Does 20 inch wheels decrease MPG?

 

No....to my knowledge the bigger you go, the better your gas mileage gets.

 

yea my mpg is horrible too and quite frankly, is pissing me off about this car. Although I am known to have a heavy foot , my gas mileage still shouldnt be as bad as it is. I always reset my trip meter when i go to the gas station and the most ive gotten on a full tank going past the empty mark 50 miles, is 280 miles. On a consistent basis, i get 260 miles going past the empty mark. This is ridiculous. 260/20 = 13 mpg!!!!!

 

I've got 20s, and a 6MT. My avg. was around 16-17 with a mix city and highway. I do beat the car up a bit. After I installed my Injen CAI, my mileage went to 19+. When not beating it up, I shift at 2-25k and I usually go from 4th to 6th. Once on the freeway, I set the cruise at the speed limit. With extended freeway driving, I've seen a peak of 28.8mpg.

BTW, I've got just over 26k miles on the car.