Gas milage help!!!

[adamw89_2000]

Ok, I know I didn't buy my hummer for fuel milage but I'm averaging 7.5 by my dic panel! Yea and I'm pretty sure it's accurate as much time as I spend at the pump... It's an 05 sut lifted 8" with 40" mud Trappists and 20x12 fuel rims. The tires are 15" wide as well. I have the cats removed which is throwing a code at the moment and I have stock gearing in it.... Is there anything I can do to this thing to get better than I am now? I'm starting to drive more and if I pussy foot it and go very slow I get almost 9... This is all in town milage for the most part. Any suggestions?

[TGCOFTN]

WOW, I could drive mine at 80-85mph and the absoulte "WORST" I have ever gotten is 13mpg. Both of mine are 100% Factory/Stock with the exception of lots of Chrome.

[Lucky1]

7.5 mpg sounds pretty normal with your set up to me. I'm stock height with 325/50/22's (35") and my computer says 10.7 and sometimes lower. I had a major tune up recently and it ran a little smoother but the gas mileage was still about the same. It has to do with aerodynamics which H2's have absolutely none ! If you own a Hummer then you have to pay to play.

[Hellz]

your running 40 inch tires!!!!

be glad you are getting 7.5mpg.

you can regear to help increase your MPG.

you can do the little mods like new spark plugs, wires, and fluids..

im running 37 inch tires and average about 8.9MPG on the DIC.

[SMITH23H2SUT]

Have you tried throwing it in neutral and coasting down every hill you come to.

[Lucky1]

Hellz is right, 7.5 mpg is not too bad for 40's with an 8" jack. Also I don't think any Hummer I've ever owned has gotten 13 mpg, not even brand new ! Lol...

[adamw89_2000]

That's not very exciting news. Lol o know rehearing may help on highway but I'm not sp sure here in town cause I'm turnin so little rpms. I will due a tune up since it is prob due but you think the code for the cats not being there is hurting it any? Maybe makin it run richer or something? Yea and these dudes r literally like driving a Brick wall down the road. Me and wind r not friends!

[HummerJim]

With the lift and the tires, that sounds pretty normal on mileage. I haven't reset the mpg on my stock H2 since I bought it new and it's stayed on either 11.1 or 11.2 mpg for the last three years.

[Indy]

Tires and windresistance will seriously lower your mpg...How much pressure are you running in the tires?

[glennf1]

Your cats removed are actually helping your mileage a little bit. You gain a little more up top but loose a little low end torque.

[adamw89_2000]

hmmm, ok wekk does not sound like much will help me then... im running my tires at 40 psi ..

[HUMTECH]

If you have no cats and your setting o2 sensor codes it will run in base fuel all the time, open loop operation. Thats whats killing your mileage.

[HUMTECH]

Larger tires will hurt mileage in stop and go traffic as it requires more throttle input to get going but will increase highway mileage as it has a taller gear ratio. Fix the "No converter problem" then see how it goes from there.

[Cesardajr]

Are you running a tuner/programmer to help recalibrate the gear ratio for the new tire size?
If not that will help, just make sure you find a tuner that can tune for the 40" tires.

[adamw89_2000]

Should I just get high flow cats or should I try and get some of those 02 sensor simulator things?? Ian not running a tuner at the moment.. U think that will help? Who makes one capable programming for a tire that big? I've though about gettin s custom time done rather than a hand held but not sure which would b better overall now.

[HUMTECH]

Simulators work good, have them on my 98 truck. If they are available for the 6l def would. If they are not available you need some cats. Ive never sourced them for a 6l so i honestly cant make that call. Google is your friend...

[tyler1bo]

Wouldn't a regear help? Like 4.88's?

[DeLH2]

I'm getting 13 on the highway and 10 in the city with lift and 37" tires. Wonder why yours is so low?

[LoJac963]

from what I read real quick the LQ4 is pretty identical to the LS2. I know when I had my GTO there were quite a few guys running O2 sims without any issues what so ever. Give the sims a shot and see if the MPG changed.

[glennf1]

If you have no cats and your setting o2 sensor codes it will run in base fuel all the time, open loop operation. Thats whats killing your mileage.

The o2's upstream *before* the cats effect fuel trim. The o2's *after* the cats have no effect on fuel trim and are only there to make sure the cats are working for emmissions.

[[__--MUD--__]]

Wouldn't a regear help? Like 4.88's?

4.88 will be less gear than stock ratio setup, 5.13 would be a little more. It would make a major improvement. I'm sure it feels like a lazy pig right now.

Honestly this rig in question is going to need $6000-10000 in additional parts to get it to drive as stock or better. Gears are $1000, Install for gears runs anywhere from $800-2000. Although not mentioned, there is no way that truck brakes now like it should now. Big Brake kits on all 4 corners start at $5000 if you get lucky. No way any of the stock steering is going to hold up for any decent amount of time. At a minumum, $1500 in steering components. To do everything your around $3500.

I really think that anyone that sells/installs lift kits should thourghly go through w/ the buyer all the additional work that will need to be done after the kits are installed. The lift kit ends up being the cheap part when you have to upgrade all these other components.

Im in the middle of putting 5.13's in my rig and im currently running 37" tires.

[HUMTECH]

Your absolutley right, pre cat o2 sensors monitor and adjust fuel trim but when the post cat sensors are not in the picture it puts the system into open loop operation and runs in a base fuel model which is always rich mixture.

[adamw89_2000]

Ive got a buddy that installe numerous gears in older card and specifically 9" fords. He's very good installer and he thinks he does not want to tackle the gears in the h2... He days he's not Forster but in some later model gm trucks you have to use a case splitter... It essentially stretched the whole bigger to get the guys out..... Anyone know if this is required on the h2s? If not we can install my gears and save me a ton of $$ . I called a well know shop and try want 2g for 4.88 installed and give me no warranty! Which I think is bs.... As far as brakes go... It's not bad, not the best but not bad.... I pull a 16ft landscaping trailer 75% of the time too... You just gotta b a smart driver.... As far as steering componets.... My front end shop assures me these front ends r not junk and can handle these wheels and setup I have.... I don't offload this truck so it's not abused by anymeans.... They suggest I keep everything lubes often and I will b fine.... They suggest I keep my stock front end until I get some wear in them before I go upgrading things.... Kits been on for 12,000 mi now and no wear yet... Only had to retighten the lift kit bolts...

[adamw89_2000]

And on the sims for the cats, any clue where these guys are buying them from? They r getting hard to find.

[Humdingah]

']4.88 will be less gear than stock ratio setup, 5.13 would be a little more. It would make a major improvement. I'm sure it feels like a lazy pig right now.

Actually going from a stock 35" tire with 4.10s to a 40" tire would require a 4.69 ratio to keep the stock ratio. Since they don't make a 4.69 you could use a 4.56 (shorter than stock) or a 4.88 (taller than stock). A 5.13 would be way taller than stock gearing...and crazy tall running 37"s.

']Big Brake kits on all 4 corners start at $5000 if you get lucky.

You can find AP Racing BBKs for roughly $4,500 front and rear if you look...and APs are just as good, if not better, than Brembos. It's the route I'm going when I put the 10-12" Cognito and 42"s on mine. But as you've mentioned previously, any lift that uses a new steering knuckle may require some creativity to mount.

']No way any of the stock steering is going to hold up for any decent amount of time. At a minumum, $1500 in steering components. To do everything your around $3500.

Agreed...$700 for the Kryptonite steering link and tie rods, $225 for the Cognito pitman and idler support brackets, $215 for the Cognito idler pivot kit and it'd be wise to upgrade the steering box and pump as 'OrangeCrush' did to his truck. An easy $1,500 to do it right provided you can do your own labor.

']I really think that anyone that sells/installs lift kits should thourghly go through w/ the buyer all the additional work that will need to be done after the kits are installed. The lift kit ends up being the cheap part when you have to upgrade all these other components.

Agreed...if you want to do it right.

']Im in the middle of putting 5.13's in my rig and im currently running 37" tires.

That's some steep-ass gearing...but not a bad idea if you plan on running bigger tires at some point.

All in all, some good advice for anyone considering lifting their truck and thinking they can bolt on a lift to the tune of $5-6,000 and be done with it. A whole lot of other things to do that most people never even give a second thought to.

:beerchug:

[Humdingah]

He days he's not Forster but in some later model gm trucks you have to use a case splitter... It essentially stretched the whole bigger to get the guys out..... Anyone know if this is required on the h2s?

You should try calling Randy's Ring & Pinion's tech line...they can tell you what's needed with a gear change in the 9.5 AAM and can also give you pricing on the gears front and rear and all of the other necessary items (shims, crush sleeves, etc).

[[__--MUD--__]]

[QUOTE=Humdingah]Actually going from a stock 35" tire with 4.10s to a 40" tire would require a 4.69 ratio to keep the stock ratio. Since they don't make a 4.69 you could use a 4.56 (shorter than stock) or a 4.88 (taller than stock). A 5.13 would be way taller than stock gearing...and crazy tall running 37"s.

I already had 4.56 gears in my truck when I bought it w stock wheels/tires. Maybe thats why I felt so much of a loss jumping up to 37's. I'm hoping w/ the extra torque I'll need less throttle which should keep it in overdrive more on the highway.

[Stellar]

Use spark plug anti foulers to remove the CEL. :beerchug:

[Humdingah]

'I already had 4.56 gears in my truck when I bought it w stock wheels/tires. Maybe thats why I felt so much of a loss jumping up to 37's. I'm hoping w/ the extra torque I'll need less throttle which should keep it in overdrive more on the highway.

:iagree:

[Indy]

Use spark plug anti foulers to remove the CEL. :beerchug:
Doesn't always work though. I would get the rear O2 sensors programmed out of the ecu for a permanent solution.

[guruerror]

Why not just put some high-flow cats in and call it a day?

[StockStar]

lifted 8" with 40" mud Trappists and 20x12 fuel rims. The tires are 15" wide as well. This is all in town milage for the most part

^ that will do it!

[adamw89_2000]

tell mw this which one is cheapest? lol i can do all the labor on any of them but im sure the sims r prob the cheapest???

[[__--MUD--__]]

Last time I bought o2 sims it was couple hundred bucks, but its been a while. o2 sims would be a bandaid and most likely trigger an occasional check engine light, editing it out of the ecm would be the fix.

[Stellar]

tell mw this which one is cheapest? lol i can do all the labor on any of them but im sure the sims r prob the cheapest???

Anti foulers. Programming your ECU and sims would be next step of course if for some reason the anti foulers don't work. But at $10 it's worth trying the anti foulers first. I have been utlizing them on my H2, Z06, Viper, and BMW and all they have all been running fine for years now with no CEL. :beerchug:

[adamw89_2000]

whwre can i get these for the 6.0

[iwillnc]

My gas mileage has went from an unmovable 11.7 to all of a sudden 12.5.... knock on wood