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Sudden Gas Guzzler

HUMMERDAD

Well-Known Member
Messages
141
Location
GraysLake IL
Has anyone had there gas milage drop. I have been avg 14gm to 16gm and all of a sudden it just droped to 10 to 12gm yes I know these are not the best on gas didn't buy it for that now with that beging said. The H2 been running fine so no tune up yet, had onstar do a dino and got nothing. My wife drives it and the last time I drove it she just seemed like she pulling a trailer. with no trailer, well I figured tune up maybe I got 14100,000 I just havent seen what all involved with the tune up on these things, other then the stander plugs, wires, fuel filter,air cleaner. Is it just that simple or is there more involved?? I had been getting around 400 miles to a tank and now she's down to 326.
 
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Pappibri

Well-Known Member
Messages
1,611
Location
Cohoctah, MI
We get the winter gas here in Michigan which I believe has more ethanol in it. But anyways, I always lose 1mpg at least due to that and plus when it gets colder your car will use a little more gas due to the choke staying open longer and more idle time.. When they put a new head on mine which includes the new injectors and they also changed the plugs and sensor and other stuff. Did nothing for my MPG. Hope you figure it out.
 

twinmill28

Spilled Milk
Messages
1,545
Location
El Centro, Mehico (Way So Cal)
Get outta town with your 14-16 numbers!! Are you running premium fuel? What's your octane?

Unless you're driving an 08 or 9 (which I can't speak to), you should only ever be getting 12 tops on a good day going downhill with a tractor trailer pushing you.
My wife can pull 12 out of our deuce (07) SOMETIMES, but mostly it's 10's and 11's for us. We've had the truck since 25K miles and have driven EVERYWHERE and it's mileage, without the travel trailer, has consistently been 10-12 and 7-10 with trailer.
 

HUMMERDAD

Well-Known Member
Messages
141
Location
GraysLake IL
Yes I avg 15.1 out here in VA where it's flat all over. No BS and on reg pump it's always been fairly good on gas considering weight to power ratio, I never expected great mileage didn't buy it for that. according to the truck it reads 14.1 She an 04 thats not been abused was a fleet viechle for the first 50,000 miles, and i don't wheel it around right now she my daily driver, thats why I was woundering if anyone has had this happen before me? I usally fillup around quater of a tank, miles are around 380 miles to 25gal of fuel. Now I am only getting 310 or less to a tank. That's why I figured a tuneup is needed but not much to change plugs wires an fuel filter from what I can find out.
 
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HUMMERDAD

Well-Known Member
Messages
141
Location
GraysLake IL
Thank you all for your replys I wound up replaceing the spark plugs and wires and add a little fuel cleaner to the tank and so far the gas milage is back up and superceding what I thought it would do. For those who are intrested E3 diamond fire spark plugs ,AC delco plug wires.
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
Glad to hear of the good results. Please be careful with the E3s. There have been engine damage issues in H3s with those plugs, though of course the H2 is a much different animal
 

Savethereef

Well-Known Member
Messages
179
Location
Long beach ca
Same here I get about 15-16mpg. Usually gas up same place too 95% of the time. When I gas up at Costco which contains ethanol my mpg drops to 11-12mpg. Also feel like there is less power. Then gas up at my regular station and back up to 15-16 mpg

BTW 87 octane
 

HUMMERDAD

Well-Known Member
Messages
141
Location
GraysLake IL
Yes califorina has that ethonal at 10% I believe the last time when I was there it stated that on the pumps. Could be off a percentage or so it's been awhile. The last time I was in town was over a year ago now. I wound up putting E3plugs and new wires in her and she's running great gas mileage has returned.
 

Big2dabank

Well-Known Member
Messages
1,216
Location
Central Florida
Before all the performance tweaks I was averaging closer to 13.5 mpg on regular pump gas. However, I can get my h2 to 16 mpg on flat ground if I baby it and drive like a grandma, but thats with the intake, headers, flowmaster exhaust, custom tune, and premium fuel. No F'n way I could drive like that every day, the truck sounds too good to baby. So, my weekly average for a tank of gas with all the tweaks is 12.3 mpg.
 

mudbug

trail blazer
Messages
232
Location
Brighton,Co
Before all the performance tweaks I was averaging closer to 13.5 mpg on regular pump gas. However, I can get my h2 to 16 mpg on flat ground if I baby it and drive like a grandma, but thats with the intake, headers, flowmaster exhaust, custom tune, and premium fuel. No F'n way I could drive like that every day, the truck sounds too good to baby. So, my weekly average for a tank of gas with all the tweaks is 12.3 mpg.

Are you running stock gears?
 
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