Terrible MPG

[BUMMER]

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?

[Big.Z.hummin]

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

[CBR_Raven]

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.

[splne1]

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.

[BUMMER]

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.

[Quijy]

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.

[Big.Z.hummin]

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?