MPG.. OUCH!

Gump2773

Original poster
Member
Feb 21, 2012
147
So, I recently purchased my 2002 TBLS, and going into it I knew I would see a mpg decrease from my previous vehicle.
HOLY SH*T! A full tank of gas nets me 190 miles. (all city) I was really hoping for close to 18 city. frustrated but I will keep a stiff upper lip
and press on.
 

MichEnvoyGuy

Member
Dec 3, 2011
522
Gump2773 said:
So, I recently purchased my 2002 TBLS, and going into it I knew I would see a mpg decrease from my previous vehicle.
HOLY SH*T! A full tank of gas nets me 190 miles. (all city) I was really hoping for close to 18 city. frustrated but I will keep a stiff upper lip
and press on.

If you are looking for good city gas mileage, Im sorry my friend but you bought the wrong vehicle!! In the winter Ive gotten as low as 13.5mpg average. :smiley_kill:
Ive owned my Envoy since 2004 and the only time I reach the window sticker mpg's is in the spring/summer/fall, a/c off, no passengers or cargo, and driving gently.
 

Matt

Member
Dec 2, 2011
4,029
You could improve that to some degree. What gear ratio do you have? Have you cleaned the throttle body? Have you put a code reader on it to see if there's any pending codes ie: O2 bank 1 sensor? How heavy is your right foot?
 

Gump2773

Original poster
Member
Feb 21, 2012
147
As far as the gear ratio... (hanging head) I have no clue. Im definately not mechanically inclined. Standard LS with 4.2 I6.
I have yet to clean the throttlebody but will be doing that today along with changing the sway bar links. As far as my driving habits go,
I have a light foot on the gas and heavy foot on the brakes. The TB has 160k on it so I tend to respect its age. a lot of vehicles die at 160k but I know my TB has a second wind to give :smile:

And as far as codes go... clean as a whistle.
 

TollKeeper

Supporting Donor
Member
Dec 3, 2011
8,143
Brighton, CO
190 miles? thats like 10 mpg or less.. Something is wrong..

I would start with a good tune up, Throttle Body cleaning, maybe a PCMFL tune..

Check on your glove box door. There will be a whole mess of 3 digit codes. GU6, GT3, or GT4 I beleive are the codes you are looking for.

I know GU6 is the 3.42 gears. Supposed to be the best for fuel mileage... I am not seeing it thou. I get 16 highway currently. I get 20's when I travel thou.
 

gmcman

Member
Dec 12, 2011
4,656
TollKeeper said:
I know GU6 is the 3.42 gears. Supposed to be the best for fuel mileage... I am not seeing it thou. I get 16 highway currently. I get 20's when I travel thou.

The 3.42 I agree would be better for hwy, but I would have to believe the 4.10 is better for city..much easier to get the sled rolling.

The 4.2 will see alot more than 160K, the trans perhaps not so much. Welcome to the club though...these things are thirsty but I feel far safer in mine than a 30 MPG Camry.
 

Matt

Member
Dec 2, 2011
4,029
Gump2773 said:
As far as the gear ratio... (hanging head) I have no clue. Im definately not mechanically inclined. Standard LS with 4.2 I6.
I have yet to clean the throttlebody but will be doing that today along with changing the sway bar links. As far as my driving habits go,
I have a light foot on the gas and heavy foot on the brakes. The TB has 160k on it so I tend to respect its age. a lot of vehicles die at 160k but I know my TB has a second wind to give :smile:

And as far as codes go... clean as a whistle.

What is the service history? When were the plugs changed and were AC Delco's used? (These trucks don't like anything else) What's your temp gauge look like after warming up? Even though it's not a true gauge, if it's sitting a tick or two left of 210, you might have a thermostat problem...that can cause bad mileage. Does your scanner read temps?
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
gmcman said:
The 3.42 I agree would be better for hwy, but I would have to believe the 4.10 is better for city..much easier to get the sled rolling.

Well my SS has the 4.10 gears and I get 9-11 city mpg's.. so how is it better? :crackup:..
 

Gump2773

Original poster
Member
Feb 21, 2012
147
I ran it down to 1/4 tank then filled it up and divided miles by gallons and Im getting 12.5 city. I changed sway bar ends yesterday but did not have time to do the throttle body or check plugs.
I will check them this afternoon as well as the gear ratio. I just kinda was shocked to see such crap mileage but i came from a 26 hwy 19 city mid size so my expectations were skewed.
I can live with it. I do feel safe in this vehicle.
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
TollKeeper said:
190 miles? thats like 10 mpg or less.. Something is wrong..

Not if he has the little fuel tank...
 

gmcman

Member
Dec 12, 2011
4,656
Boricua SS said:
Well my SS has the 4.10 gears and I get 9-11 city mpg's.. so how is it better? :crackup:..

Are you serious?


Your 6.0 is just maybe more thirsty than my 4.2. :duh:

:thumbsup:
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
I just swapped from 3.73 to 4.10 so I will see how it affects my mileage
 

ItsOnVoy

Member
Nov 21, 2011
2,401
Boricua SS said:
Well my SS has the 4.10 gears and I get 9-11 city mpg's.. so how is it better? :crackup:..

:suicide::puke: damn but hey I would take that SS over this any day! Worth the extra gas to have some fun with that truck :yes:

HARDTRAILZ said:
I just swapped from 3.73 to 4.10 so I will see how it affects my mileage

Stupid question but does that give your truck more speed? If so how do you swap it and how much did it cost you if you don't mind me asking?
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
ItsOnVoy said:
Stupid question but does that give your truck more speed? If so how do you swap it and how much did it cost you if you don't mind me asking?

Speed...no. Likely my top speed is less. Better take-off maybe, but I dont rip on my truck except offroad. It was done for me to make up for the larger tires.

I have more money than most would in the swap. I bought the axle...which I have seen from $500 to $1000...then I bought an open carrier ($150) and a LockRight locker ($400ish) since the SS limited slip is junk to me and my use. I would have incurred another $200-$300 expense for swapping the carrier and installing locker had I not had friends to let me help them do it.

The swap is as simple as unbolting everything and bolting it back up. The brakes are interchangable from SS to standard and all mounts are the same. The only issue is I need to shorten my driveshaft even with my extended control arms and lift. I do not think you could install the driveshaft at all without my mods. I only have 1/2 inch of play. The driveshaft also requires a bastard ujoint $25 since the SS and regulars use different ones. It is all in my thread on my swap.
 

Voymom

Member
Feb 3, 2012
2,523
I have the 3.73 gear ratio in my 4.2L I6 Envoy and its the extended wheel base(LWB) so I have the 3rd row seat. I'm managing about 15.2 MPG, but that's an overall average. I get roughly 394 miles a tank in Phantom. It doesn't seem to last me very long but I for one have a very heavy right foot, and we do a lot of driving through town. I was getting about 10mpg's city or less a few weeks ago, but making some slight changes has helped a ton. We have set the trip A to get a rough estimate of how many miles to a tank and it was under the 394 I can say that, and that was driving mostly highway.

My Buick Rendezvous which was the biggest POS SUV I have ever owned got really decent fuel economy, 18 city and 22 hwy. BUT like I said it was a giant POS! In my opinion it will be quite difficult to find a full size/mid size SUV that does get good gas mileage. You bought a vehicle that stays around 13-15mpg average...and gas prices are supposed to go up once again this summer. All these things should be considered before purchasing a truck/SUV. I didn't take fuel economy into consideration when I made my purchase. It costs me about $75.00 a tank and I have to fill up 3x a week and that's using the mid grade fuel(Silver) which happens to be cheaper here as it has more ethanol. But I was in for a HUGE meltdown at the fuel pump when I bought Phantom. I thought for sure the fumes were messing with me, but no...the fuel economy really does suck that bad in these platforms. And the price of gas definitely doesn't help.

That stiff upper lip will soften eventually lol I too had to hold a stiff upper lip and keep trucking when that first tank of gas was needed. But I fell so madly in love with my truck, that fuel economy no longer matters. Sometimes I wonder why I never bought this truck in the very beginning, then I wouldn't have had to deal with that Buick I traded it in for lol You will LOVE your truck in the long run trust me on that.

Btw: I'm not sure if this really plays much of a difference. But how warm is your truck running? I heard if the t-stat is shit and your running to rich, it could put a damper on your fuel economy. Someone correct me if i'm wrong though. I just changed my t-stat (well watched hubby do it) and we will see if it helps our fuel economy as we were running rich at around 165 degrees. Now i'm just waiting for my husband to fix the big UH OH he made last night while putting the ALT back on :crazy:
 

ItsOnVoy

Member
Nov 21, 2011
2,401
HARDTRAILZ said:
Speed...no. Likely my top speed is less. Better take-off maybe, but I dont rip on my truck except offroad. It was done for me to make up for the larger tires.

I have more money than most would in the swap. I bought the axle...which I have seen from $500 to $1000...then I bought an open carrier ($150) and a LockRight locker ($400ish) since the SS limited slip is junk to me and my use. I would have incurred another $200-$300 expense for swapping the carrier and installing locker had I not had friends to let me help them do it.

The swap is as simple as unbolting everything and bolting it back up. The brakes are interchangable from SS to standard and all mounts are the same. The only issue is I need to shorten my driveshaft even with my extended control arms and lift. I do not think you could install the driveshaft at all without my mods. I only have 1/2 inch of play. The driveshaft also requires a bastard ujoint $25 since the SS and regulars use different ones. It is all in my thread on my swap.

Oh wow seems like it cost quite a bit! But the switch was for your off roading pretty much! I read on the OS once that switch would give the truck more speed which is why I asked! Ill look into your thread!
 

TB360

Member
Dec 29, 2011
169
Gump2773 said:
As far as the gear ratio... (hanging head) I have no clue. Im definately not mechanically inclined. Standard LS with 4.2 I6.
I have yet to clean the throttlebody but will be doing that today along with changing the sway bar links. As far as my driving habits go,
I have a light foot on the gas and heavy foot on the brakes. The TB has 160k on it so I tend to respect its age. a lot of vehicles die at 160k but I know my TB has a second wind to give :smile:

And as far as codes go... clean as a whistle.

At 160K miles, you're vehicle is still a baby. Just keep the maintenance going and our vehicles could last for a while. There is a thread on other sites about "how many do you have?" and you will be surprise that there are some that are almost 300K now. With 4.2 size engine, expect that 18 MPG would almost be impossible especially on city driving. It all depends on driving habits.
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
gmcman said:
Are you serious?


Your 6.0 is just maybe more thirsty than my 4.2. :duh:

:thumbsup:

I know man.. was just goofing on you.. I modded as well.. so I'm nowhere near the 13-15 city/17-19 highway mpg's...

ItsOnVoy said:
:suicide::puke: damn but hey I would take that SS over this any day! Worth the extra gas to have some fun with that truck :yes:

Which is exactly why I bought it... you only live once.. and I'm having fun doing it! :yes:
 

ItsOnVoy

Member
Nov 21, 2011
2,401
Boricua SS said:
Which is exactly why I bought it... you only live once.. and I'm having fun doing it! :yes:

Couldn't agree more man!!
 

djthumper

Administrator
Nov 20, 2011
14,955
North Las Vegas
ItsOnVoy said:
Oh wow seems like it cost quite a bit! But the switch was for your off roading pretty much! I read on the OS once that switch would give the truck more speed which is why I asked! Ill look into your thread!
Not necessarily top speed, It will get you up to speed quicker than a 3.42 will.
 

RayVoy

Member
Nov 20, 2011
939
Your going to get a lot of suggestions on what is wrong, but a short list with the biggest bang is this one.

Change/check all of the following:
- change the plugs (use Delco),
- change the air filter,
- change the front O2 sensor (the rear one just checks the cat),
- change the oil to synthetic,
- check the air in the tires (bring it up to the PSI on the door sticker and add a couple, or 3 PSI more),
- check the alignment of all tires.

I didn't add the throttle body, you know about it.

Look at the temp gage on the dash. The temp needle should be straight up (210), this is the first check on the T-stat.
 

gmcman

Member
Dec 12, 2011
4,656
ItsOnVoy said:
:suicide::puke: damn but hey I would take that SS over this any day! Worth the extra gas to have some fun with that truck :yes:?

Oh absolutely...the only other option when I bought mine was the 5.3 and that was in the limo version. I still enjoy the I6 though.

Would really enjoy a SS.
 

christo829

Member
Dec 7, 2011
505
Fairfax, Virginia
Add to Ray's list the differential fluid. If you've got 4wd, rear *and* front, as well as making sure the transfer
case fluid has been changed. You can't always assume the previous owner did maintenance at the proper
intervals. Transfer case fluid should have been getting changed every 50K mi. Differentials at 100K mi, for normal
usage.

Also, check the transmission fluid. Does it look nice and clean, clear red? If not, might be time for a fluid and
filter change. With that many miles, don't go for a flush, just do the pan drop fluid and filter swap.

Ray's list will have the most direct effect, but after that, anything that can affect the driveability can lower the mpg.
Drag in the drivetrain from poor lubrication (diffs/tc) or poor hydraulic performance (trans) can make the engine work
a lot harder to get the same amount of work done.

Good Luck!

Chris
 

gmcman

Member
Dec 12, 2011
4,656
ItsOnVoy said:
Oh wow seems like it cost quite a bit! But the switch was for your off roading pretty much! I read on the OS once that switch would give the truck more speed which is why I asked! Ill look into your thread!

Granted this isn't a SS by any means, but is bone stock. I can't give it a hard flat-foot on the gas since my 3-4 clutches are on their way out..don't want to abuse it too much, but I think the accel is decent for running 87. I drove a 3:73 and it was nice but the 4:10 is slightly "snappier"

This is with the 4:10, total dog between 45-55 after the shift though, when I get the trans rebuilt I will add in a tune for sure. So if you are contemplating a switch I personally wouldn't have another one unless it had a 4:10.

Had to ease up at 5500 in fear of a full-throttle 2-3 shift, didn't want to walk home...:no:

[video=youtube;rhblyqKubIc]http://www.youtube.com/watch?v=rhblyqKubIc[/video]
 

gmcman

Member
Dec 12, 2011
4,656
Boricua SS said:
I know man.. was just goofing on you.. I modded as well.. so I'm nowhere near the 13-15 city/17-19 highway mpg's...



Which is exactly why I bought it... you only live once.. and I'm having fun doing it! :yes:

I figured you were :cool:
 

ItsOnVoy

Member
Nov 21, 2011
2,401
gmcman said:
Granted this isn't a SS by any means, but is bone stock. I can't give it a hard flat-foot on the gas since my 3-4 clutches are on their way out..don't want to abuse it too much, but I think the accel is decent for running 87. I drove a 3:73 and it was nice but the 4:10 is slightly "snappier"

This is with the 4:10, total dog between 45-55 after the shift though, when I get the trans rebuilt I will add in a tune for sure. So if you are contemplating a switch I personally wouldn't have another one unless it had a 4:10.

Had to ease up at 5500 in fear of a full-throttle 2-3 shift, didn't want to walk home...:no:

[video=youtube;rhblyqKubIc]http://www.youtube.com/watch?v=rhblyqKubIc[/video]

It is still a good 8 seconds to get to 60 MPH. Mine gets that also and I have the stock 3:73
 

gmcman

Member
Dec 12, 2011
4,656
ItsOnVoy said:
It is still a good 8 seconds to get to 60 MPH. Mine gets that also and I have the stock 3:73

Yeah I would say right about 8 or just a tick under. If I powerbrake it slightly it will be under 8 but not doing that right now for sure. These engines pull hard after 4500 so if it doesn't have to shift then that adds for some good accel numbers when rolling. Off the line is good and towing is good, 50 MPH roll on with a 3.42 or 3.73 would be interesting, they keep pulling and I have to shift.
 

Sparky

Member
Dec 4, 2011
12,927
Gump2773 said:
So, I recently purchased my 2002 TBLS, and going into it I knew I would see a mpg decrease from my previous vehicle.
HOLY SH*T! A full tank of gas nets me 190 miles. (all city) I was really hoping for close to 18 city. frustrated but I will keep a stiff upper lip
and press on.

I get 18 on my 02 LS on an upper average tank (mostly highway with city thrown in for good measure).

All out highway 20-21.

All out city, well, that's the pits. I've not done 100% city but it's gonna suck...
 

gmcman

Member
Dec 12, 2011
4,656
Sparky said:
I get 18 on my 02 LS on an upper average tank (mostly highway with city thrown in for good measure).

All out highway 20-21.

All out city, well, that's the pits. I've not done 100% city but it's gonna suck...

Haven't tested a full city tank either but my numbers are about the same as yours.
 

ItsOnVoy

Member
Nov 21, 2011
2,401
Sparky said:
I get 18 on my 02 LS on an upper average tank (mostly highway with city thrown in for good measure).

All out highway 20-21.

All out city, well, that's the pits. I've not done 100% city but it's gonna suck...

well i would get about 12-13MPG but I just had my fuel filter replace and throttle body cleaned and injectors cleaned etc. So going to see if it gets any better I hope!
 

Gump2773

Original poster
Member
Feb 21, 2012
147
Just did another test. Ran down to 1/4 tank, filled up and divided miles by amount filled. 10.99 mpg. UGH:hissyfit:
All city miles. Still have not completed any maintenance. Will start this week. And as well, my temp gauge never goes 210, Always a tick or 2 left of center.
All of this depresses me. :confused:
 

gmcman

Member
Dec 12, 2011
4,656
Straight up is 210, not 195. A tick to the left is about 195, I don't understand how 210 is 195.

I hear that alot but 195 is normal. You would need to verify with a scan tool that will read live data and see what is being read by the ecm. If it shows 195 then you are fine. Did you check to see of the cat is pluged?
 
Feb 24, 2012
133
Is your check engine light on? Are you sure the torque converter is locking up? What are your tire pressures?

The higher your ethanol ratio the worse your milage will be.

The good news is this group will help you get to the bottom of your problem.


Sorry this is at your expense, but this whole thread makes me feel much better about my truck!
 

Voymom

Member
Feb 3, 2012
2,523
My truck ran at times a tick or 2 left of center(210) but it also ran cooler than that at times as well. My husband kept saying it was fine, and normal and everyone here said to change the t-stat. After a few days of arguing lol I finally got hubby convinced to just change the stupid thing. When we finally got a warm day and changed it, the truck ran so much better, and has not ran any less than 210, not even a tick lower. The T-stat was a PITA to change with having to deal with the ALT, but it was cheap. I think I paid $32.00 for a brand new OEM 190 t-stat from OReilly's.

I know it sucks finding all of these things out, but you shouldn't expect anything less from a used vehicle in my opinion. Even my truck which I bought from a dealership needed a bunch of regular maintenance work. A lot of people/places think that keeping tire pressure up to par and regular oil changes is the only regular maintenance vehicles need, but that just isn't true...there is a lot more to it than just waxing and driving. I still need to get my sway bar links done...which is decently priced, but I'm guessing those too will be a PITA to change lol.

So far I have learned that simple or so called simple fixes on at least my truck....always end up not being so simple. For example, my T-stat change ended up costing me about $75.00 because my wonderful husband decided to somehow cut my ALT connector, and as always we had to order it from a dealership, and as always they charged us out of the butt for the part....which we found online for less than $20.00 which included shipping :lipsrsealed:

I have a few things of regular maintenance that I still need to get done...at least 6 more things. And I have only had the truck for a month :redface:
It definitely sucks, but in the end I can promise it will be all worth it!
 

RayVoy

Member
Nov 20, 2011
939
There are some parts on these trucks, that when we talk about them, we don't say if it fails, we say "WHEN" it fails.

Four that immediately come to mind, are:
1- Ignition switch
2- End-links
3- AC compressor clutch bearing
4 - T-stat
 

northcreek

Member
Jan 15, 2012
3,334
WNY
I went from a Tahoe to a Mercury Mariner(first Ford ever) to save on gas.Under 50k and two transmission jobs later I'm back to a real truck,apparently that enormus 16' ski boat of mine was to much for that "soccer mom's Suv" .
I'm getting 16mpg around town and will glady pay it now.When I think of the $$ that I wasted on that POS, repairs,sales taxes,etc. I could have bought an SS,run Hi-test,drove with the E-brake on and still been money ahead...Mike.:hissyfit:
 

Gump2773

Original poster
Member
Feb 21, 2012
147
Well, I appreciate all of you listening to my groans as I try to straighten all this out. My total love for the truck hides the real frustration. Man I would cut a leg off for 16 mpg.
Maybe a couple fingers for 14. Heh.. My tired TB needs Viagra.
 

jham

Member
Nov 20, 2011
1,334
Gump2773 said:
Just did another test. Ran down to 1/4 tank, filled up and divided miles by amount filled. 10.99 mpg. UGH:hissyfit:
All city miles. Still have not completed any maintenance. Will start this week. And as well, my temp gauge never goes 210, Always a tick or 2 left of center.
All of this depresses me. :confused:

1/4 tank and only 11 gallons. I just filled mine at a 1/4 tank and it took 16 gallons
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
Where did it say he put in 11the gallons

jham said:
1/4 tank and only 11 gallons. I just filled mine at a 1/4 tank and it took 16 gallons
 

Gump2773

Original poster
Member
Feb 21, 2012
147
jham said:
1/4 tank and only 11 gallons. I just filled mine at a 1/4 tank and it took 16 gallons

11 gallons? The 10.99 is the miles per gallon i filled 14.6 gallons at just below 1/4 tank.
 

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