picked up a 2003 Yukon XL 2500

[jeep-N-montero]

347/37 = 9.37 ?? I thought that was average for the 8.1 with 6.0s supposed to be getting 12-14?

That was the readout when driving around town in 20 degree weather, pretty sure engine/sensors were not even warmed up at the time. Saturday I checked the tire pressure and all were under 40, aired them up to 60 and definitely felt a difference in rolling resistance. Looks like the plugs and wires will arrive today and tomorrow with the intake setup arriving later in the week, should see quite an improvement as it has never had the plugs/wires replaced with 127k original miles on the truck.

 

[Martinjmpr]

347/37 = 9.37 ?? I thought that was average for the 8.1 with 6.0s supposed to be getting 12-14?

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If it's city driving that doesn't surprise me. Stop-and-go city driving is a killer for a heavy vehicle like this. Get it on the highway and keep it rolling and it will do pretty decently on MPG.
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But if you're in traffic? Forget it. Every time you stop and start again you've got to get nearly 3 tons of sheet metal moving - that's going to use a lot of fuel.
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That's why I got an R50 Pathfinder as my DD. Even in stop and go city driving I still get 16 - 18 MPG. Even with my 'Burb being a half-ton vs. the OP's 3/4 ton, and having "only" the 5.3, I can barely break 14 MPG in city driving (12 is the EPA rating) So 10 MPG in the city for a 2500 is absolutely believable to me.

 

[Martinjmpr]

Those OBC's typically are very conservative in the calc. It's probably 347 till E light comes on. That should leave few gallons in the tank.

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While that's generally true I've found the OBC (On Board Computer for those not familiar with the acronym) for my Suburban is surprisingly accurate. Even more so than the Scangauge II in some instances, which is odd because I can calibrate the SGII but not the OBC. Nevertheless there have been times when the MPG calculated by the SGII was way off and the OBC was much closer to what my fuel consumption figured as.
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Speaking of OBCS, On our recent AZ trip I was a little bit risky with my fuel ups. Since I search for the cheapest gas I can get I tend to push my fuel stops as far as possible from each other. That led to at least two occasions where I put just over 31 gallons in my 31 gallon tank! In both cases the OBC said I still had about 25 miles of fuel left (which would be roughly 2 gallons when pulling the trailer) so I need to be more careful of that in the future.
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It's one thing to run out of gas because all the gas stations on your route are closed (that happened to us in 2012 driving through Oregon - because Oregon does not allow self-service gas, gas stations in small towns close at night since it's not worth it for them to keep an employee there) but it's pretty stupid to run out of gas when you have driven by several gas stations and just not stopped there because you thought there was cheaper gas a little further down the road. I've learned my lesson and will plan accordingly for the future!

 

[p nut]

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While that's generally true I've found the OBC (On Board Computer for those not familiar with the acronym) for my Suburban is surprisingly accurate. Even more so than the Scangauge II in some instances, which is odd because I can calibrate the SGII but not the OBC. Nevertheless there have been times when the MPG calculated by the SGII was way off and the OBC was much closer to what my fuel consumption figured as.
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Speaking of OBCS, On our recent AZ trip I was a little bit risky with my fuel ups. Since I search for the cheapest gas I can get I tend to push my fuel stops as far as possible from each other. That led to at least two occasions where I put just over 31 gallons in my 31 gallon tank! In both cases the OBC said I still had about 25 miles of fuel left (which would be roughly 2 gallons when pulling the trailer) so I need to be more careful of that in the future.
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It's one thing to run out of gas because all the gas stations on your route are closed (that happened to us in 2012 driving through Oregon - because Oregon does not allow self-service gas, gas stations in small towns close at night since it's not worth it for them to keep an employee there) but it's pretty stupid to run out of gas when you have driven by several gas stations and just not stopped there because you thought there was cheaper gas a little further down the road. I've learned my lesson and will plan accordingly for the future!

Yikes. All OBC's I've had had at least 20-30 miles of buffer. My Ford has around 4 gallons at 0 DTE!
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I've always learned to fill up at 1/4 tank, especially on road trips. Too many times, I've been too far below the "E".

 

[jeep-N-montero]

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If it's city driving that doesn't surprise me. Stop-and-go city driving is a killer for a heavy vehicle like this. Get it on the highway and keep it rolling and it will do pretty decently on MPG.
.
But if you're in traffic? Forget it. Every time you stop and start again you've got to get nearly 3 tons of sheet metal moving - that's going to use a lot of fuel.
.
That's why I got an R50 Pathfinder as my DD. Even in stop and go city driving I still get 16 - 18 MPG. Even with my 'Burb being a half-ton vs. the OP's 3/4 ton, and having "only" the 5.3, I can barely break 14 MPG in city driving (12 is the EPA rating) So 10 MPG in the city for a 2500 is absolutely believable to me.

Yikes. All OBC's I've had had at least 20-30 miles of buffer. My Ford has around 4 gallons at 0 DTE!
_
I've always learned to fill up at 1/4 tank, especially on road trips. Too many times, I've been too far below the "E".

My DD is a Mazda 3 that gets 30+mpg, the Yukon will not see much use outside of hauling duties or Christmas shopping so mpg is not a huge issue, but if I can manage to get 14+ it will be nice.

 

[Martinjmpr]

My DD is a Mazda 3 that gets 30+mpg, the Yukon will not see much use outside of hauling duties or Christmas shopping so mpg is not a huge issue, but if I can manage to get 14+ it will be nice.

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On the freeway without a lot of stop and go I would imagine 14 would be easy. As I said, it's the stop and go that gets you. And the idling and waiting for a light to turn green.
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BTW when do we get to see pictures? You're killing us here. :sombrero:

 

[Chili]

My Z71 with the 5.3 averaged mid 10's to mid 11's around town, and up to maybe 15 on the highway if I kept speeds reasonable. The small lift, larger MT tires and front and rear Ranch Hand bumpers killed my mileage.

Bone stock I got like 18 on a road trip once, keeping it under the speed limit the whole time.

 

[jeep-N-montero]

My Z71 with the 5.3 averaged mid 10's to mid 11's around town, and up to maybe 15 on the highway if I kept speeds reasonable. The small lift, larger MT tires and front and rear Ranch Hand bumpers killed my mileage.

Bone stock I got like 18 on a road trip once, keeping it under the speed limit the whole time.

This thing will be staying stock, so no lift or aggressive tires, have the Montero for playing in the dirt.

 

[Ramblejam]

I wanted it more so for 'pick-up' when passing, climbing steep grades, and the like.

I was trying to get across that there just isn't a big difference between the two; the 6.0L is just a bored-out 5.3L. Have the 2004 specs in front of me here...

5.3L: 3.78" bore, 3.62" stroke
6.0L: 4" bore x 3.62" stroke

As one would figure from those numbers, output is a little higher on the six liter, but peak torque RPM is the same on both @ 4000.

Seems like guys on here try to sell these as some sort of SUV panacea, but (as the owner of one), I'd have to disagree; they are terrifically versatile though. Like a "jack of all trades, master of none".

.Every time you stop and start again you've got to get nearly 3 tons of sheet metal moving - that's going to use a lot of fuel.

+1 on that.

GM put curb weight at 5800. Real world numbers (like the link posted below) are up at 6300. I've ran mine across the scale empty (other than fuel/basic supplies), and was a bit above that.

At the end of the day, it's a small-block, naturally-aspirated gas engine...there's only so much it can do. Throw high(er) 3.73 axle gearing into the mix, 4L80E ratios (like the 2.48 first), a truck full of people/gear and a trailer in tow, and folks (especially those coming from modern turbo diesels) aren't terribly pleased.

http://media.caranddriver.com/files...-expedition-gmc-yukoncall-of-the-canyon-4.pdf

My Z71 with the 5.3 averaged mid 10's to mid 11's around town, and up to maybe 15 on the highway if I kept speeds reasonable. The small lift, larger MT tires and front and rear Ranch Hand bumpers killed my mileage.

Yep. While modern turbo-diesels with massive off-idle torque have a bunch of leeway (for lifts, bigger tires, etc.), you really have a tight range with these before falling out of optimum operating conditions/range.

 

[jscusmcvet]

Looking forward to what you do here and the results you get from the aftermarket parts. I still keep my eyes open for a nice 2500 that I could pick up and still hold onto my LJ. Best of luck with this rig.

 

[jeep-N-montero]

Looks like the truck was a good boy and got a few gifts a bit early.

 

[jeep-N-montero]

Changed the oil and swapped in the Airaid last Thursday, other than a tiny bit of whistle at WOT it is nice and quiet. Also discovered where the very slow coolant leak is at, the weep hole on the WP is the culprit, I was planning on a new pump anyway and am glad it wasn't the radiator. Once it gets warmer I will swap in the pump and flush the radiator.

 

[jeep-N-montero]

Installed the Hypertech programmer Monday evening and seems to feel a bit more "peppy", still need to play with adjusting the shift points for better mpg. Also ordered the new water pump and hoses.

 

[rayra]

Yikes. All OBC's I've had had at least 20-30 miles of buffer. My Ford has around 4 gallons at 0 DTE!
_
I've always learned to fill up at 1/4 tank, especially on road trips. Too many times, I've been too far below the "E".

It's also a good way to avoid burning up a fuel pump too, as seems to be a frequent problem with running a Suburban around on 'E' all the time.

Too there's a website / app called 'GasBuddy', it's a crowd-sourcing sort of thing that shows all the stations around you and their current prices. The map portion of the app even shows brands with the prices. It DOESN'T however show Costco or SamsClub fuel pricing / locations. It's a great little app that takes the guesswork out of where to shave a couple bucks.

 

[Martinjmpr]

It's also a good way to avoid burning up a fuel pump too, as seems to be a frequent problem with running a Suburban around on 'E' all the time.

Too there's a website / app called 'GasBuddy', it's a crowd-sourcing sort of thing that shows all the stations around you and their current prices. The map portion of the app even shows brands with the prices. It DOESN'T however show Costco or SamsClub fuel pricing / locations. It's a great little app that takes the guesswork out of where to shave a couple bucks.

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Oh yeah, been using GasBuddy for years. The double edged sword is that it can tempt you to try to stretch your fuelups: "If I go 20 more miles I can save a dime a gallon!"