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Hello,

Does anyone know what would cause me to be getting horrible gas mileage for the past few weeks. Normally I average around 28-30 mpg (I get this number from the onboard computer console thing in the radio). However the past 2 weeks I have been getting horrible gas mileage 22-23 mpg. This problem started after I got my car back from the dealer for the problem detailed here

http://www.g6ownersclub.com/forum/showthread.php?t=763

Does anyone know what I can look into to find out what might be causing this problem? My tires are properly inflated and I don't let my car run for anymore than 1 minute to warm up. Plus I have been randomly resetting my mpg calculator and it always comes up with about the same average. I was thinking that when they replaced the battery control module they didn't program it right so there's not enough power going to the sparkplugs because the car seems much more sluggish than it was a month ago. I don't know, I'm planning on driving it for another week with a fresh tank of gas to see if that helps and if not I'm taking it back to the dealer, which will be the fifth time in 3 months. yuck!

Perhaps car’s don’t get the same gas mileage they do when it’s cold out (below 30) than they do when its warmer. I’m not sure since this is my first car with an mpg calculator in it. Please Help!
 

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problazer said:
Hello,

Does anyone know what would cause me to be getting horrible gas mileage for the past few weeks. Normally I average around 28-30 mpg (I get this number from the onboard computer console thing in the radio). However the past 2 weeks I have been getting horrible gas mileage 22-23 mpg. This problem started after I got my car back from the dealer for the problem detailed here

http://www.g6ownersclub.com/forum/showthread.php?t=763

Does anyone know what I can look into to find out what might be causing this problem? My tires are properly inflated and I don't let my car run for anymore than 1 minute to warm up. Plus I have been randomly resetting my mpg calculator and it always comes up with about the same average. I was thinking that when they replaced the battery control module they didn't program it right so there's not enough power going to the sparkplugs because the car seems much more sluggish than it was a month ago. I don't know, I'm planning on driving it for another week with a fresh tank of gas to see if that helps and if not I'm taking it back to the dealer, which will be the fifth time in 3 months. yuck!

Perhaps car’s don’t get the same gas mileage they do when it’s cold out (below 30) than they do when its warmer. I’m not sure since this is my first car with an mpg calculator in it. Please Help!

It may be the weather!

I was getting 28-30 mpg before, and lately, 22-23 (in the sedan, but i had higher numbers a few weeks ago).

My commute hasn't changed. My driving habits are...well...just as bad. :p But the only variable factor has been the temps.
 

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problazer said:
Plus I have been randomly resetting my mpg calculator and it always comes up with about the same average. Perhaps car’s don’t get the same gas mileage they do when it’s cold out (below 30) than they do when its warmer. I’m not sure since this is my first car with an mpg calculator in it. Please Help!
personally, i wouldn't sweat it. you say that you "randomly" reset your "mpg calculator" and you have been having this problem for the past two weeks. just how many times have you 'reset' it in this two week period? the computer is going to calculate your mileage from the point you reset it and if you are doing it more frequently than at each fill-up, you're probably not getting a very good 'average' reading. say for instance you reset it and drive 20 miles in stop and go traffic. your mpg will drop. but if you reset it each time you fill up, you get a better avereage as you will have more than likely driven at higher, non-stop speeds during that period.

i would recommend that you just reset your computer every time you fill up and make sure you reset ALL the data to ZERO. this will give you a better indication of your actual mpg. as for the cold weather, it would be my guess that this is also a factor, regardless as to how long you allow your car to warm up.
 

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Noone mentioned the fact that you generally get worse mileage with winter gas due to the additives to keep water out. I always get worse mileage in the winter, although you should have been pumping it for alot longer than a couple weeks.

I know older cars will runch richer until the engine gets up to temp, I don't see why new ones would be any different.
 

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I usually never averaged below 31mpg all summer long and all of a sudden one day it started dropping rapidly. I hadn't changed driving habits and nothing was out of the ordinary. By the time it got down to 25mpg I decided to reset the average since I hadn't done it for the past 6000 miles or so. It continued to stay around 25-26 and all of a sudden one day it climbed back up into the 30's. I didn't have time to figure the mileage on paper to see what I was really averaging but I wouldn't put too much trust it the DIC.

One day I started the car and my clock was 2hours slow and the temp was reading in *C instead of *F. On my way to work it decided to change back to *F but the clock was still wrong so I reset it. Hopefully that doesn't happen again. :(
 

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G6Action said:
personally, i wouldn't sweat it. you say that you "randomly" reset your "mpg calculator" and you have been having this problem for the past two weeks. just how many times have you 'reset' it in this two week period? the computer is going to calculate your mileage from the point you reset it and if you are doing it more frequently than at each fill-up, you're probably not getting a very good 'average' reading. say for instance you reset it and drive 20 miles in stop and go traffic. your mpg will drop. but if you reset it each time you fill up, you get a better avereage as you will have more than likely driven at higher, non-stop speeds during that period.

i would recommend that you just reset your computer every time you fill up and make sure you reset ALL the data to ZERO. this will give you a better indication of your actual mpg. as for the cold weather, it would be my guess that this is also a factor, regardless as to how long you allow your car to warm up.
I normally only reset the statistics whenever I fill up and that is what I have been doing for a while until I noticed that my mpg was off. I guess I shouldn't have said I was "randomly resetting it" What I should have said was that I will reset it before I leave for work, which is mostly highway driving to see if there was any improvement from the day before.

From what I have read from the other posts, I think the additive to the gas probably explain my problem. I guess I just never noticed it before because I never had the tools to easily check my mpg with the push of a button.

If anyone has any other idea's I'm definatly open to hearing them though!
 

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problazer said:
I normally only reset the statistics whenever I fill up and that is what I have been doing for a while until I noticed that my mpg was off. I guess I shouldn't have said I was "randomly resetting it" What I should have said was that I will reset it before I leave for work, which is mostly highway driving to see if there was any improvement from the day before.

From what I have read from the other posts, I think the additive to the gas probably explain my problem. I guess I just never noticed it before because I never had the tools to easily check my mpg with the push of a button.

If anyone has any other idea's I'm definatly open to hearing them though!
i would imagine that everything posted to your question is a contributing factor. and your comment about 'never having the tools to easily check your mpg with the push of a button', all i can say is that generally 'a little knowledge can be very dangerous'!!!! ha ha unless you religiously calulated your mileage on your old car, you probably wouldn't have noticed a 4 or 5 mpg decrease.

hey, just blame it on new technology!!! :D
 

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Oxygenated gas? Um, can you explain that?

Where do you live? As temperatures decrease the gas becomes more dense. ie. there are more molecules in a litre/gallon. The computer will read it accordingly.

Example: If you fill up your tank all the way to the top at -10 degrees, then put your car in a garage the fuel will expand and possibly leak out.

Does you car go faster when its cold? It should cause there is more stuff to burn in each spray of fuel.
 

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If you are driving through snow that doesnt help either. The gas mileage in my old Grand Am went down about 9mpg in the winter! Its gone down in the G6 too. I haven't reset the gas mileage in a couple of months so I'm not really sure how much it has changed. Haven't calcualted it by hand either, but my best guess is about 6-8 on the highway and about 3-4 in the city.
 

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rwbooth said:
As temperatures decrease the gas becomes more dense. ie. there are more molecules in a litre/gallon.
I didn't do well in chemistry, but I was pretty sure you can't compress liquids.

I'd say your loss in gas milage is due to a couple of things. 1. When the engine is cold, it'll idle a little faster to warm up. 2. Running your defroster (A/C) is a big guzzler. 3. Be sure to check your tire pressure! (air does compress)
Also, I'd calculate your milage with pencil and paper a few times to see how accurate the DICs really are. I haven't checked my G6 yet, but the one on my Grand Prix was terrible.
 

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Yes, it is mostly due to the weather and the fact that the remote start will idle higher in the winter. Your car would run faster in the winter because of the dense air, more oxygen = more fuel demand.
 

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rwbooth said:
Oxygenated gas? Um, can you explain that?
.
There are different formulas for gasolines sold by state and region. Different additive packages for pollution adn cold weather. Most will affect MPG.
 

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Weller said:
I didn't do well in chemistry, but I was pretty sure you can't compress liquids.

I'd say your loss in gas milage is due to a couple of things. 1. When the engine is cold, it'll idle a little faster to warm up. 2. Running your defroster (A/C) is a big guzzler. 3. Be sure to check your tire pressure! (air does compress)
Also, I'd calculate your milage with pencil and paper a few times to see how accurate the DICs really are. I haven't checked my G6 yet, but the one on my Grand Prix was terrible.
Liquids don't compress per se, but the density changes. In the winter 2 gallons of gas will have more mass than in the summer. Essentially, 2 gallons of gas in the winter is more gas than 2 gallons in the summer.

As far as tire pressure and A/C they generally do not affect mileage much. I've read some reports where they have tested these things and they've been shown not to affect much. For the tire pressure test they filled the tire to 10 PSI below the recommended level. They found it only reduced the mpg by about 2. The Mythbusters tested the A/C on a track with Ford Explorers. They found that the difference between windows down and A/C was minimal.

All this stuff refers to summer time though. I don't know how much winter would change these things.
 

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Lucius said:
Liquids don't compress per se, but the density changes. In the winter 2 gallons of gas will have more mass than in the summer. Essentially, 2 gallons of gas in the winter is more gas than 2 gallons in the summer.

As far as tire pressure and A/C they generally do not affect mileage much. I've read some reports where they have tested these things and they've been shown not to affect much. For the tire pressure test they filled the tire to 10 PSI below the recommended level. They found it only reduced the mpg by about 2. The Mythbusters tested the A/C on a track with Ford Explorers. They found that the difference between windows down and A/C was minimal.
I don't know where you learned that from (maybe on TV too?) but the density of a liquid does not change due to temperature. Density=Mass/Volume. The Ideal Gas Law, PV=nRT, applies to gas, not gasoline. Here's an experiment for ya, take a gallon of water and sit it out on your counter and measure how full it is. Then put the jug in the fridge for awhile and remeasure it. It doesn't change. You can pick any temp between the boiling and freezing points and it won't change.
You're saying tire pressure isn't much of a factor? You just said it decreased their mpg by 2. Problazer said he went from 29 down to 23. Looks like that's about 1/3 of what he lost.
I wasn't comparing the A/C to the windows being down. I was comparing the defroster (A/C) to heat (vent) windows up.
 
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