2004 gmc envoy slt XL bad mpg?

2004gmcenvoy

Original poster
Member
May 5, 2012
10
I have a 2004 envoy slt xl with 79,xxx miles, and its been getting about 12.7 mpg when it used to get about 15.7 mpg. This is mostly city driven. Sinced the water pump and thermostat broke down its been 12.7 mpg. The water pump, thermostat, coolant temp sensor, ac delco plugs, fuel pressure regulator, k&n air filter, fuel filter, ac deco o2 sensor has been changed to new ones but still not improving the mpg. I also put in some fuel cleaner too but still not improving. I clean the throttle body too but samething. Im planning to change out the cat converter or just cut it off. What else should I do next?
Any input will help, thanks.
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
2004gmcenvoy said:
I have a 2004 envoy slt xl with 79,xxx miles, and its been getting about 12.7 mpg when it used to get about 15.7 mpg. This is mostly city driven. Sinced the water pump and thermostat broke down its been 12.7 mpg. The water pump, thermostat, coolant temp sensor, ac delco plugs, fuel pressure regulator, k&n air filter, fuel filter, ac deco o2 sensor has been changed to new ones but still not improving the mpg. I also put in some fuel cleaner too but still not improving. I clean the throttle body too but samething. Im planning to change out the cat converter or just cut it off. What else should I do next?
Any input will help, thanks.

is that calculated mpg's, or are you going off the DIC? i know the DIC's arent accurate... but it sounds like you have covered all the basics aas far as mpg's go... im sure others will chime in for ideas... hope you figure it out...
 

2004gmcenvoy

Original poster
Member
May 5, 2012
10
Boricua SS said:
is that calculated mpg's, or are you going off the DIC? i know the DIC's arent accurate... but it sounds like you have covered all the basics aas far as mpg's go... im sure others will chime in for ideas... hope you figure it out...

Im going by the dic, but i just fill up a couple days ago. Ill see how many mile itll get out of a full tank.
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
2004gmcenvoy said:
Im going by the dic, but i just fill up a couple days ago. Ill see how many mile itll get out of a full tank.

yea, its better to go with true calculations... in my DD my DIC said i was getting 31.2 mpgs on a 3 hour drive.. but when i did the calulations, i was really only getting 27.7 mpgs....
 

CaptainXL

Member
Dec 4, 2011
2,445
2004gmcenvoy said:
I have a 2004 envoy slt xl with 79,xxx miles, and its been getting about 12.7 mpg...This is mostly city driven.

Others as well as I get about 13 MPG in the city with our XL's so I would say you are good. My highway calculated mileage is 18 MPG. I would calculate your highway mileage and let us know what that is. With properly inflated tires it should be around 18 or 19.
 

2004gmcenvoy

Original poster
Member
May 5, 2012
10
Ok the envoy XL got 330 miles out of a full tank. This is all city driven, never hop on the freeway. I believe its a 25 gallon tank on the 04 envoy xl, thats about 13.2 mpg city driven. But wouldnt it be a little better than 13.2mpg? The dic saids im getting 12.9 mpg. Fill up the gas tank and got 22 gallons only?
 

Blckshdw

Moderator
Nov 20, 2011
10,657
Tampa Bay Area, FL
2004gmcenvoy said:
Ok the envoy XL got 330 miles out of a full tank. This is all city driven, never hop on the freeway. I believe its a 25 gallon tank on the 04 envoy xl, thats about 13.2 mpg city driven. But wouldnt it be a little better than 13.2mpg? The dic saids im getting 12.9 mpg. Fill up the gas tank and got 22 gallons only?

Sounds about right, I get about the same distance on a full tank, with primarily city driving. That needle will get really low, and the low fuel light usually comes on when you've got about 2 gallons left.
 

2004gmcenvoy

Original poster
Member
May 5, 2012
10
Blckshdw said:
Sounds about right, I get about the same distance on a full tank, with primarily city driving. That needle will get really low, and the low fuel light usually comes on when you've got about 2 gallons left.

Yeah, i keep going by the dic thats what throws me off. Well i only used 22 gallons on this tank so i get about 15mpg city driving. Im going outta state next week, ill see how much mpg highway ill get.
 

Blckshdw

Moderator
Nov 20, 2011
10,657
Tampa Bay Area, FL
I always go calculated, only way to be sure. I average about 15.5 give or take, higher of course if I spend time on the freeway. I have a scangauge, and keep an eye on the average/instant MPGs from that, tends to be MUCH more accurate. :twocents:
 

cody_s

Member
Dec 6, 2011
625
Atlanta, GA
Also, if you're looking at the average on the DIC, and not the instant, you want to reset the system. Not sure how far back it averages from, but it's probably averaging your current MPG with what it was before you replaced things.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
cody_s said:
Also, if you're looking at the average on the DIC, and not the instant, you want to reset the system. Not sure how far back it averages from, but it's probably averaging your current MPG with what it was before you replaced things.

My Envoy was about 5 years old before I reset the average MPG on the DIC.
 

2004gmcenvoy

Original poster
Member
May 5, 2012
10
Ok i got 400miles out of a full thank until the low fuel light came on. 70 percent highway and 30 percent city. Got 18.1 mpg, topped off with 22 gallons when emptied.
 

CaptainXL

Member
Dec 4, 2011
2,445
2004gmcenvoy said:
Ok i got 400miles out of a full thank until the low fuel light came on. 70 percent highway and 30 percent city. Got 18.1 mpg, topped off with 22 gallons when emptied.

For an XL 18 mpg is excellent considering your mileage is not all highway.

What gear ratio do you have? I have the 3.42 GU6
 

2004gmcenvoy

Original poster
Member
May 5, 2012
10
CaptainXL said:
For an XL 18 mpg is excellent considering your mileage is not all highway.

What gear ratio do you have? I have the 3.42 GU6

Im not sure what gear ratio i have, never look into it. I guess my mpg wasnt all that bad probally because i was doing mostly city driving most of the time.
 

seanpooh

Member
Jan 24, 2012
461
I get ~450 miles on a tank full. I can fill up close to 26 gallons when I'm done driving with the Empty light on for ~20 miles (I see the blue tinge from the gas out the tank). It's 90% highway and country roads (20-40 minutes per trip).

On 12 hour trips the DIC says I can go 600miles on the tank :eek:

Your XL is getting great mileage.

Of the 10 years and ~120K miles (I never knew it could be reseted until this year), the average miles per gallon was 15.2 mpg. Techron and seafoam does help.
 

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