Terrible MPG
 

Ok ok, I know this is a very heavy vehicle, AWD, Big engine etc etc but how in the world am i averaging only 7.8 mpg?? I just had a tune-up, replaced a Catalytic converter, new alignment and new tires, I'm on stock wheels too. I know I should be averaging better mileage considering Im easy on the pedal. What would be the first things to check?

Re: Terrible MPG
 

maybe air intake filter? i know i went for long time forgetting to replace it and when i did i gained a whole mpg back

Re: Terrible MPG
 

Are you towing or hauling anything really heavy?
Do you let the truck sit and idle for long periods of time?
Are you driving mostly city or highway?

If you're doing mostly city driving then you could very well average in a range from 7mpg to 10mpg...if you're towing/hauling anything heavy, that will make a big decline in MPG as well...also, letting the truck sit at idle for long periods of time will affect the average MPG.

I'm averaging 12.1MPG right now with a mix of city and highway driving...however, I've seen my MPG decline badly when I'm doing any of the things I mentioned above.

Re: Terrible MPG
 

I think we have all said this before, ITS A HUMMER!!!! We don't drive them for MPG or we all would be in a prius!! LOL J/K bustin your nutz anyhow check your MAF sensor and air filter you could be running to lean or to rich.

Re: Terrible MPG
 

Thanks for the replies fellas, the recent tune up did replace the air filter and am running AC delco plugs. I am doing alot of stop and going driving but I still find it hard to believe the MPG can be this bad. I checked my average last night and now Im averaging 7.5 My most recent fillup was with BP 89 Octane.

Re: Terrible MPG
 

After I tuned the ECM, Magnaflow and CAD I am at 11mpg city solid on 87 fuel and 14 to 15 mpg highway depending on terrain and weather on 87 fuel.

Re: Terrible MPG
 

i'm at 10.3 currently and thats with m/t's oversized brushguard and gobi rack. i always run 89 octane because maybe its just me but i feel a huge difference between low and mid grade. when i run 87 my engine sounds like its working overdrive and screams up hills. maybe it just mine. anyone else experience that?

Re: Terrible MPG
 

with a stock truck, i have never gotten worse than like 9.8, thats with me just driveing the hell out of it, and when my wife drives, she gets low 11,s this is average mpg..

this is stock, with 35 inch M/Ts..

Re: Terrible MPG
 

I would have to agree that 7.5 mpg is pretty bad, when we had our 2006 we got 10.5-11.5 with mixed driving (majority of it around town) depending on weather obviously being worse in the winter with letting the truck warm up etc.... On the highway we got 13-14.5 depending on cruising speed. So far with the 2008 it looks like we are getting closer to 12 with the majority in town (short trips) but I have only run 1 tank of fuel since getting it a few weeks back.

Re: Terrible MPG
 

Do you think the AC delco plugs could be causing such bad MPG? Which OEM brand did the 2003's come with from the factory?

Re: Terrible MPG
 

I know you said you were on stock wheels but do you have stock tires?

I'm not trying to play semantics but taller tires will make you lose 2-3 mpg.

Mark

Re: Terrible MPG
 

Mark, my tires are stock BFG's. My mpg today went up a bit from 7.5 to 7.9 lol

Re: Terrible MPG
 

Man, you need to check air filter, plugs, etc.... I know H2's get ****ty gas mileage but I didn't get that kind of mileage unless I was towing a trailer running 75+ with big tires and a supercharger.


Mark

Re: Terrible MPG
 

I don't get that bad of mileage pulling my 23' boat. Something is wrong. See how helpful I am......not. :lame:

Re: Terrible MPG
 

Mine gets 12 mpg with Toyo open country mud tires . Yours is got a problem ,or your driveing habits need to change (LED FOOT) if you think it is bad now wait till gas is $5.00 a gallon .

Re: Terrible MPG
 

I am averaging 13.1 mpg and I mash it as much as possible! I only got 14 on my 6.0L Denali, that proves the H2 is an amazingly efficient engineering marvel. I remember the instant mileage display that GM used on older trucks, I could get it down to 4 mpg:clapping: Try resetting the mileage thingy! that always helps!

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