Lets Get This Party Started

[Tyrone Harward]

I purchased a 2008 GMC Yukon XL 1500 5.3L Flexfuel SLT. This is going to be the daily driver for my wife to haul around my 4 children for the foreseeable future. Along with being the daily driver, it will be used for going camping in the Southwest and hauling a boat or trailer. With these in mind, and I want to get as many miles out of every component as possible. I would like to make aftermarket mods which will help me achieve these goals. I would like to get 300k+ miles out of this vehicle. Some of my concerns. Heat. I live. St. George Utah. It gets and stays 100+ most of the summer and we travel to Phoenix AZ regularly in the summer, so heat is a major factor. Fuel Economy. I know this is not a Prius but I would like my modifications to increase mpg as well. I am mechanically inclined but do not have access to a lift just jack stands and so nothing crazy like replacing cams ok. Mods should be pocketbook sensitive, try to keep them under $500 and have a purpose. If the purpose is it makes it sound cool, well I'm not twenty and I already have a hot wife and 4 children so I get all the action I want. I am totally up for listening to suggestions. I have a couple in mind and will be posting them as I go along.

 

[gpracer1]

Get a tune first.
It should have come from the factory with a tune, it will drive and shift much better.

 

[kbuskill]

Looks like @gpracer1 beat me to it.

Definitely get a tune.

Also you should check your RPO codes on the sticker in the glove box because you may already have some of the "mods" you are talking about.

Oil cooler and transmission cooler are both options from the factory. Look for K5L on the RPO list as that is the "enhanced cooling" package.

Also your truck should already have dual electric fans... unless someone removed them for some strange reason.

 

[08HoeCD]

Yeah, getting a Blackbear Performance tune is an excellent move. It will increase power a bit and may even add 1 or 2 mpg to fuel economy. More important, it will provide an enhanced shift schedule which will reduce the transmission’s gear-shift slippage, which will reduce heat and wear. Makes the vehicle much more responsive and much more pleasant/fun to drive.

 

[intheburbs]

+1 on the tune, but it'll most likely make your mileage worse because it'll be more fun to drive.

Regarding mileage improvements, like the entrance to Hell says, "Abandon hope all ye who enter here." It's a gas-guzzling American SUV. Not much you can do to improve mileage, except maybe switching to a tire with a very hard compound and low rolling resistance. CAFE has forced the automakers to push the envelope to get the most mileage possible, so cheap and easy tweaks aren't really there.

My 3/4-ton Burb gets 15 on the highway, if I really feather the gas. My Sierra Denali gets 12 around town.

 

[swathdiver]

I purchased a 2008 GMC Yukon XL 1500 5.3L Flexfuel SLT. ...Mods should be pocketbook sensitive

Decode your RPO sheet on the glovebox door, you may already have most of these. Look for K5L, KNP, KC4, G80, GT4 or GT5, etc.

++on the Tune! You're going to have to decide on whether or not you want to turn off AFM/DOD for greater reliability or keep it on for the mileage. After the fun wears off, the tune usually increases mileage over and above what you were getting with AFM active.

Did you get the service records of this truck? If not, you can use the CarFax to see where it was serviced previously, and kindly ask each business for the maintenance records to be emailed or faxed to you.

Buy a Tech2! It's more important than your favorite set of wrenches, for without it, you may not know which wrench to use!

When I bought mine this is what I did:

All Service Items (100k service)
Tech2
Tires
BlackBear Tune

Ohh, is that 'Burb 2WD or 4WD?

 

[Tyrone Harward]

Thanks For all the replies. This is great!

Wish I would have known about the glove box door. I was going old school and getting dirty under the hood.
I do not have a transmission cooler.I did order one from B&M
I will double check the fan.
I did pull the carfax, great advice, service seems to be pretty good. I have not thought about calling and having the records sent to me a great idea.
I will move the tune to the top of the list. From what I gathered If I get the Auto Cal Tune black Bear I can retune if I was to make any additional mods.
At first, I was excited about the AFM for the millage but after getting on the forum it seems to cause more problems in the long run and not that much improvement on mileage.

Thanks again for all the useful advice.

I will keep this thread updated on the progress.

 

[Tyrone Harward]

Finally had time to break down all the RPO Codes in the Glove box.
This was not supper exciting but very informative. IF you see something I miss identified please let me know. I highlighted the ones I wanted to reference quickly or had questions on.

 

[Tyrone Harward]

2nd battery?
Obviously It can be done. That's not the question. The question is. Is the wiring harness in my Yukon already setup for it? I have read both views it seems to depend on the trim or options. I do have the trailer package and from what I have gathered that seems to be the distinguishing feature. IF it is setup for it already how do I go about it and what part do I need? OR do you know a link or video for it? Thanks for the assistance. If you are wondering why. Dependability.

 

[swathdiver]

It seems to me you're missing codes, U and K are ones that stuck out. Otherwise it looks like you have a nicely equipped 2008 Yukon XL with 4WD.

There are various ways to wire up a second battery. You can do it like the diesels or the main method is to have this run be independent of the other battery for starting purposes, this second one would run accessories and or whatever is hooked up to the trailer wiring. There are write up here and on other forums by members who have done it here. The GM Upfitter's Guides also discuss this.

@intheburbs @Doubeleive are two that come to mind that have installed the second battery.