Gas mileage issues ( REALLY BAD) - Page 2 - Pontiac G6 Forum
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post #16 of 30 (permalink) Old 12-16-2010, 10:54 AM
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i have that same problem, however my gas mileage isnt as bad but its not good. Dealer said everything is running fine O2 sensors etc. found a small leak in one strut and starting to see wear on my axle seal but nothing fuel economy related. i dont know what to do either. my car can be sluggish at times too. let me know what you find out.
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post #17 of 30 (permalink) Old 12-16-2010, 07:02 PM
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o and i tried the torque convertor test it would only rev to 200k rpms. not sure what tht means for my car tho in your previous post didnt quit say. What did you get when you tested yours?

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post #18 of 30 (permalink) Old 12-17-2010, 01:19 AM
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Originally Posted by goodguy_69 View Post
Thank u for the info. I will try this tomorrow.
i had the car in since my last post. They had the car for 4 days and a tech took the car home, back and forth... I told them that I wanted them to drive the car the way I do in the city. They claimed that the driver drove city with a bit of driving on a parallel rd to the freeway and that he put 60kms on it each way which was 120k a day.
need less to say they got 400 kms on a 1/2 tank and they said that was normal... They were sitting at 7.8l per 100 k. and the avg speed was 35kms.
I found that interesting and said that it is impossible for them to be driving it in town as I have NEVER got that EVER. They told me that the cause is the "shorter in town Trips" Because, I do not drive to work everyday and that when I do go out I am going to say 15- 20 kms. The other thing they claimed is to much idling. Well I can tell you I am not in the HABIT of sitting in my car and letting it r
I took the car back and tried driving a little different, Every time I started going out I tried to use the hwy as much as I could. Gas was a bit better but the 35miles per hr started dropping. and the consumption started rising. Then I thought, This is crazy. I am adding extra time to every trip and going out of my way to try and get "good In town Gas consumption".
I since filled the car and started driving it back the way I "normally do" and I am back to the crappy numbers, In city 250kms on a full tank. and the avg speed has dropped to 25.
I had my mother try a little test. She drives her 98 Malibu 6 cyl the same way that I drive my G6. Actually she takes shorter trips. Only going to the food store and back every other day and she is getting 500kms on a tank which is 56.8 ltrs.
So there theory of it being because of Shorter driving tips is a load of BS.
I was wondering if it is possible that driving between 50k and 60k if the TCC could be burning an access amount of fuel?
I know that when I had the transmission issue that it was hitting hard and chugging around 50kms and if I was on the hwy and pressed down on the gas it would chug. That's when they replaced the transmission, But I do not have any of those issues now as far as chugging or " Hitting hard when it shifted around 50k" but am wondering if it is not consuming to much gas when being driven in that range?

I will however try the converter test tomorrow and advise.
If anyone else may have some other suggestions that would be great.

Thanks
Hmmm. I know how the dealership can be, when addressing problems that are not easy to solve. The first thing out of their mouth is always, "it's your driving style" or "they're all like that" or "it's characteristic of the vehicle."
I went through a similar nightmare with Honda a couple years back. But I stayed on them with a vengeance until they corrected every single problem.
As long as it's not to your liking, keep bringing it back. I assume that you are under warranty??
Unfortunately, you may have to do a little leg work yourself, to get them headed in the right direction.

Let's check some things. You have the 3.5 V6 right?
Does your radio have the trip computer included?
What does the display show your AVG MPG @ right now?
Using the INSTANT MPG, track what your mpg is at various (steady) speeds.

At a steady 35mph, 50mph, 60mph, 70mph? I've always been very impressed with the 3.5's highway economy. At 65 you should see, atleast 26mpg on the display. 28-30MPG is what I've always seen indicated at those speeds.

In spirited, city driving. I *always* get 17 or 18mpg indicated by the trip computer. This is on *every* recent GM 3.5, 3.8, 3.9V6 I've driven. If I am more sparing with the throttle, I may see 19mpg indicated for city driving.
So I can see how city mpg could be a little low. But on the highway, these engines, with their healthy low end torque and tall gearing, really shine (rarely falling below 26 MPG AVG).

These are things you may have to do (but your dealer should have already):
Jack up each wheel and make sure it spins freely, without drag.
Check your tire pressure.
I'd replace the fuel filter.
Run a quality fuel system treatment through the gas tank.

Did this car ever get good mileage? Give it a good listen for any strange sounds from the engine and tranny. Both should be relatively smooth.

You say the dealer got 7.8lpk? Whoah! I just converted that... 30.1 mpg!! No way. In the city? That's just bs, for sure.

I got my best results with the dealer by taking the service technician on a ride with me and pinpointing each of my problems. The ride was NOT over until he confirmed that he could see/hear exactly what I saw and heard.

Verify that your trip computer is somewhat (they are rarely perfect) accurate. Pick out a test loop (near the dealer). At the beginning of the test route, reset the computer. At the end, note the mileage. We already know that you're gonna get less than the claimed 30.1 mpg the dealer claimed.
Repeat the procedure, but this time with the dealers tech driving. If there's no problem, his numbers should be considerably higher than yours. And that's with a similar driving style, driving normally, not trying to artificially raise the mpg.

But if he get's bad numbers too, pin him down on it and stay on them until they fix it to your satisfaction.

The other thing though... there's gonna be variation in every engine design. In a perfect world all G6 3.5's would get the same mileage under the same conditions. But in reality power, mpg and driveability can vary by a considerably large margin from engine to engine while being in perfectly good shape. Your particular engine may just be one that is gonna deliver low mpg. It happens.

But 11mpg is outside of any margin that could be considered normal. That's extreme. Did it get good mileage before? Ever?

Did you get this car used? Beware that there is a good chance that a used G6, may have been a RENTAL CAR in it's former life. That in itself opens up a whole can of worms. Rental cars get regular service, but they also have a hard service life.
They come off the delivery truck and go straight to the rental lot with, often, less than 2 miles on the odometer. Then they are rented and immediately taken on 500+ mile freeway trips non stop. Or they get thrashed around town. A NEW engine needs a proper break in, if it is to produce respectable mpg, power, and reliability over it's lifetime. Long trips with steady rpms is not good for a virgin engine. High rpm, high throttle is not good for a virgin engine. But this is exactly the kind of service these fleet units see. Even a regular used car may not have been treated well before you received it. Just something to thing about.

So many factors can effect your mpg. Yes, it's gonna be hard to find out what the problem is. But the dealer should acknowledge the problem AND be most helpful in resolving it.

Keep us posted.
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post #19 of 30 (permalink) Old 12-17-2010, 02:29 AM
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After reconnecting my battery (I replaced several of the under-hood wire loom covers) my consumption meter was reset. After a week of pure city-only driving, I'm running about 15 mpg. This is nearly 15 l/100k. On an economy run, I have been able to get 33 MPG / 7 l/100k driving for 62 miles (100k) setting the cruise for a constant 61 mph (basically 100k). The consumption dropped a bit at 67 mph by about 2.5 MPG.

This is with a G6 GT with the 3.5 l engine. The GT has lower gearing and thus the consumption is higher than the G6 non-GT or the 4-cylinder engine. With a typical tank of fuel, I average around 18.7 MPG (12.8 l/100k) as most of my driving is city. I usually behave pretty well, but we have a lot of 'smart streets' that are actually pretty stupid, so I spend a lot of time idling.

~ MattInSoCal
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post #20 of 30 (permalink) Old 12-17-2010, 04:25 PM Thread Starter
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Quote:
Originally Posted by thakid22 View Post
Verify that your torque convertor is transmitting power properly. You don't want excess slippage there.

At idle, in Drive, briefly apply and hold the brake.
While the brake is fully depressed, the push the throttle to the floor, until the revs stop climbing. The engine should groan steadily for a bit.

Your tachometer should show about 2400rpm, at the most, during this test. If you see 3000, 3200, 4000rpm, then you've got a slipping torque converter. If you can only raise it to 1200rpm or so, you have a converter that is too "tight" or low engine output.

With the brakes fully pressed, the car shouldn't move when you hit the gas. But do it in a safe place just in case. Don't hold the brake and gas down together for more than 10 seconds.

Only do this with the engine and tranny fully warmed up. That's the only test of the torque converter that you can do yourself... besides just feeling for it's operation.
I tried this test today and got 2000rpm...
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post #21 of 30 (permalink) Old 12-17-2010, 07:13 PM Thread Starter
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Originally Posted by thakid22 View Post
hmmm. I know how the dealership can be, when addressing problems that are not easy to solve. The first thing out of their mouth is always, "it's your driving style" or "they're all like that" or "it's characteristic of the vehicle."
i went through a similar nightmare with honda a couple years back. But i stayed on them with a vengeance until they corrected every single problem.
As long as it's not to your liking, keep bringing it back. I assume that you are under warranty??
Unfortunately, you may have to do a little leg work yourself, to get them headed in the right direction.

Let's check some things. You have the 3.5 v6 right? yes
does your radio have the trip computer included? yes
what does the display show your avg mpg @ right now? 18.9ltrs per k
using the instant mpg, track what your mpg is at various (steady) speeds.

At a steady 35mph, 50mph, 60mph, 70mph? I've always been very impressed with the 3.5's highway economy. At 65 you should see, atleast 26mpg on the display. 28-30mpg is what i've always seen indicated at those speeds. i will try this

in spirited, city driving. I *always* get 17 or 18mpg indicated by the trip computer. This is on *every* recent gm 3.5, 3.8, 3.9v6 i've driven. If i am more sparing with the throttle, i may see 19mpg indicated for city driving.
So i can see how city mpg could be a little low. But on the highway, these engines, with their healthy low end torque and tall gearing, really shine (rarely falling below 26 mpg avg).

These are things you may have to do (but your dealer should have already):
Jack up each wheel and make sure it spins freely, without drag.
Check your tire pressure.
I'd replace the fuel filter.
Run a quality fuel system treatment through the gas tank. i have not done any of these things to date, but i will try and do by early next week and advise

did this car ever get good mileage? i cannot say, i bought the car with 20,000 k on it and i also owned a f-150 8cyl, i used to drive both. So when i got in one and it needed gas i put it in. But never tracking it. I sold my f-150 and am only driving my g6 and this is the reason i am noticing it now. I also must say that i owned my truck for 6 yrs and only used that for a period of 4 yrs and got way better consumption in it. Interesting fact is i drove my truck the same way that i drive my car. Mostly in town. give it a good listen for any strange sounds from the engine and tranny. Both should be relatively smooth. sounds normal

you say the dealer got 7.8lpk? Whoah! I just converted that... 30.1 mpg!! No way. In the city? That's just bs, for sure. yes... They claimed that it was considered city driving... I told them they were full of crapola... They are not driving it the way that i am and that they cannot tell me they drive 60kms one way to work and not be on the freeway.

i got my best results with the dealer by taking the service technician on a ride with me and pinpointing each of my problems. The ride was not over until he confirmed that he could see/hear exactly what i saw and heard.

Verify that your trip computer is somewhat (they are rarely perfect) accurate. Pick out a test loop (near the dealer). At the beginning of the test route, reset the computer.i have done this and it is almost accurate. Not far off. They did tell me tho that you cannot go by the gages on the dash for mpg/ltrs as they are never correct. Funny thing with this is they are out by maybe 1 mpg when i do thenumbers for consumption from my receipts. at the end, note the mileage. We already know that you're gonna get less than the claimed 30.1 mpg the dealer claimed.
Repeat the procedure, but this time with the dealers tech driving. If there's no problem, his numbers should be considerably higher than yours. And that's with a similar driving style, driving normally, not trying to artificially raise the mpg. i will need to do this as well

but if he get's bad numbers too, pin him down on it and stay on them until they fix it to your satisfaction.

The other thing though... There's gonna be variation in every engine design. In a perfect world all g6 3.5's would get the same mileage under the same conditions. But in reality power, mpg and driveability can vary by a considerably large margin from engine to engine while being in perfectly good shape. Your particular engine may just be one that is gonna deliver low mpg. It happens.

But 11mpg is outside of any margin that could be considered normal. That's extreme. Did it get good mileage before? Ever? see answer above

did you get this car used? yes. Bought it from the dealer with 20,000k on itbeware that there is a good chance that a used g6, may have been a rental car in it's former life. That in itself opens up a whole can of worms. Rental cars get regular service, but they also have a hard service life. uggh... Scary...
they come off the delivery truck and go straight to the rental lot with, often, less than 2 miles on the odometer. Then they are rented and immediately taken on 500+ mile freeway trips non stop. Or they get thrashed around town. A new engine needs a proper break in, if it is to produce respectable mpg, power, and reliability over it's lifetime. Long trips with steady rpms is not good for a virgin engine. High rpm, high throttle is not good for a virgin engine. But this is exactly the kind of service these fleet units see. Even a regular used car may not have been treated well before you received it. Just something to thing about.

So many factors can effect your mpg. Yes, it's gonna be hard to find out what the problem is. But the dealer should acknowledge the problem and be most helpful in resolving it.

Keep us posted.

i wanted to thank you for all your info... I have some homework to do and that is fine..at least i am not going to twiddle my thumbs not knowing what to do cause the dealer is not being helpful. I will post results when i have them.
I have responded to your posting through out it in bold caps so that you can see the answers.

Thanks again
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post #22 of 30 (permalink) Old 11-19-2012, 06:30 AM
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Hi!

I was jsut wondering if the problem was solved. I'm having the same problem with my 2007 G6 V6 SE. I'm doing about 20L/100 KM (about 11Mpg) and it started to do this about 5 months ago and can't find out why... I used to do about 13L/100KM (I think around 18/20 MPG) and I can't pin point the problem.

Any updates on this situation?

Thanks!
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post #23 of 30 (permalink) Old 11-19-2012, 12:21 PM
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Seems odd. I read that you're filling the tank half way. Fill it all the way to get a much more accurate reading.

I get about 400kms on a tank of fuel, with about 1/4 tank left. Most of my driving is in town. I use the autostick regularly (stay within 2500-3500rpm) and the few tanks that I had calculated last year set me in the 12-14L/100km range depending on traffic. Straight highway I can get 600km and if I wanted to, I could squeeze another 100kms in but I like to have a decent reserve. I drove to Pearson airport and back (190km) and I put in 16L to top it up which wasn't bad for a 115km/h stint.

If anything else just do a full tune up on the car. Make sure the air intake isn't blocked, new plugs, tire pressures are at proper pressure, and running synthetic oil can lower frictional loss. I run Amsoil 5W30 full synthetic in my G6 and change the oil every 1-2 years as I only put on about 8-10K miles a year. Not all bad/faulty O2 sensors will throw a code right away either.

It goes to show that it's always good to check your mileage.

'11 Ram SXT 4x4 quad cab - 5.7L V8; 128,200kms
'09 Malibu 2Lt 3.6L - 140,000kms purchased 1 March 2019

'06 Pontiac G6 GT - 3.5L V6; 162,000kms (rear ended 15 Feb 2019, and given totalled title by insurance)
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post #24 of 30 (permalink) Old 11-20-2012, 01:35 PM Thread Starter
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Gas Issue

Hi,
The answer is No, I never did get to the bottom of it and then I had enough and sold the car. The dealership could only say that they felt that it was a issue of city driving...

Quote:
Originally Posted by Ziggy450 View Post
Hi!

I was jsut wondering if the problem was solved. I'm having the same problem with my 2007 G6 V6 SE. I'm doing about 20L/100 KM (about 11Mpg) and it started to do this about 5 months ago and can't find out why... I used to do about 13L/100KM (I think around 18/20 MPG) and I can't pin point the problem.

Any updates on this situation?

Thanks!
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post #25 of 30 (permalink) Old 11-20-2012, 05:28 PM
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Wow! Talk about good customer service!

Sad to say but this will probably be my first and last american car... or GM... dunno yet. I'll try taking a look at the O2 sensor and see if this fixes at least part of the problem..
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post #26 of 30 (permalink) Old 11-21-2012, 05:05 AM
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GM's customer service experience for me was similar, but not over mileage. It'll take a lot for me to get another new GM vehicle. Only reason I went with GM was I had all these GM Visa points, plus the incentives on Pontiac at the time made it a steal. I got what I paid for, ha.

'11 Ram SXT 4x4 quad cab - 5.7L V8; 128,200kms
'09 Malibu 2Lt 3.6L - 140,000kms purchased 1 March 2019

'06 Pontiac G6 GT - 3.5L V6; 162,000kms (rear ended 15 Feb 2019, and given totalled title by insurance)
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post #27 of 30 (permalink) Old 11-22-2012, 12:37 AM
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Yea I also got incentives and a nice deal my G6. Second car ever. Also second GM. I've had absolutely no major issues with either car. I'll always be a GM fan, always.

But that doesn't mean I won't buy other makes. I'm looking for a project drift car as soon as my G6 is paid off

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post #28 of 30 (permalink) Old 07-11-2013, 05:03 PM
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hey goodguy_69, are you still getting terrible gas mileage? I'm in the same situation as you are.. i only get about 120-150kms from full to half with mixed city/highway driving. Let me know.
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post #29 of 30 (permalink) Old 02-18-2014, 03:14 AM
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Poor Gas Mileage

I had an 2008 Chevy Impala LT1. I had the 3.5 in it. I got 19 city & 28-34 Hwy. I totaled car.

I bought a used Pontiac G6 SE V6 3.5. I'm getting 14/15 city & 23 hwy. I read all the posts & still don't know why I can't get the same gas mileage as my 08 Impala?

I had it checked out by a few dealers & they can't find anything. It sucks.
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post #30 of 30 (permalink) Old 11-09-2018, 01:03 PM
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I'm hoping its an ECT sensor that's causing this, I'm having the same issue an have done everything but ECT will try and let you guys know the fix!
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