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I have a 2005 Hummer H2 with 55,000 miles on it. Last year I put a 6" lift on it with 38" tires. I realize that Hummer's do not get great gas mileage to begin with and the lift did not help, but I am currently getting about 4 MPG with the truck. It has been this way for about 5-6 months now. When I first lifted the truck this was not the case. Any suggestion/explanation for this?

Submitted: 112 days and 5 hours ago.

Category: Car

Value: $15

Status: CLOSED

Year: 2005
Make: Hummer
Model: H2
Engine: Vortec Supercharger/Volant Cold Air In-Take

Already Tried:
Cleaned the air filter, normal maintenance (regular oil changes etc)

Posted by GM Tech 112 days and 5 hours ago.

Info Request

Welcome. Did you recalibrate the speedometer for the larger tires?

112 days and 5 hours ago.

Reply

No, because there is a Vortec Supercharger on the truck it has been "chipped" with a tuner. I however do not have the tuner and have been trying to find a way to re-program the truck. I cannot use another tuner because it must be returned to stock first. Also, the engine needs special tuning for the supercharger for the timing and all the other stuff that goes into making that work. Do you have any suggestions on how i can go about having that done? Can someone hook it up to a computer or something?

Posted by GM Tech 112 days and 5 hours ago.

Answer

OK, the mileage is likely because you are truly traveling farther than the odometer reads so the mileage is not as bad as you think. You will want a custom programming that will fix all these together. Try THIS site.

112 days and 5 hours ago.

Reply

That may be true, but when i map quest the mileage to my destination I am filling up about every 170 miles. I'm just having a terrible time believing that i am only getting 170 miles to the tank. I know that when i first lifted the truck it was no where near that bad.

Posted by GM Tech 112 days and 5 hours ago.

Answer

It may be time to review the calibrations then. Something has changed that is causing this.

112 days and 5 hours ago.

Reply

How can that be done? Putting a new custom program on the truck? Do you think that getting that bad of gas mileage sounds like there might be something wrong or should i just accept it?

Posted by GM Tech 112 days and 5 hours ago.

Answer

How do you drive? Are you aggressive? With that much power and something lifted as you have it, I know I would drive very aggressive. Also do you do much highway or is it mostly city driving?

112 days and 5 hours ago.

Reply

Mostly highway. I dont drive too aggressive cause i know it just complicates my gas problem. When driving on the highway around 60-70mph the truck will go from about 2.5 rpm's to like 4-5 real hard with no inputs from me to try and get back up to whatever speed i was driving to drive at.

Posted by GM Tech 112 days and 5 hours ago.

Info Request

What condition are your tires in? Are they worn, under inflated, over inflated?

112 days and 5 hours ago.

Reply

About 10,000 miles on them, great tread still. They are not swampers either, just a toyo all-terrain. They are inflated to the PSI that the tire requires, i just checked this about a week ago.

Posted by GM Tech 112 days and 4 hours ago.

Answer

OK, Unless we can go back to stock and evaluate the mileage from there, it will be really hard to know what and where to chase. Also we are at a point that we would need a scan tool to see what all the readings from the sensors are.

112 days and 4 hours ago.

Reply

Where/how would you suggest i go about fixing this? Should I try to have a custom program put on it?

Accepted Answer

I think a custom programming would be the place to start with the mods you have done to this truck. Just for the heck of it, can you post a picture of your ride?

Accepts:
Expert:	GM Tech
Pos. Feedback:	98.7 %
Answered:	8/2/2009

Auto Service Technician

Lead technician, GM Grand Master Technician 2007. 9 years Automotive experience, 7 years with GM

112 days and 3 hours ago.

Reply

Thank you sir and I will post a picture shortly.

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Optional Information

Year: 2005
Make: Hummer
Model: H2
Engine: Vortec Supercharger/Volant Cold Air In-Take

Already Tried:
Cleaned the air filter, normal maintenance (regular oil changes etc)

Info Request

Welcome. Did you recalibrate the speedometer for the larger tires?

Reply

Answer

OK, the mileage is likely because you are truly traveling farther than the odometer reads so the mileage is not as bad as you think. You will want a custom programming that will fix all these together. Try THIS site.

Reply

That may be true, but when i map quest the mileage to my destination I am filling up about every 170 miles. I'm just having a terrible time believing that i am only getting 170 miles to the tank. I know that when i first lifted the truck it was no where near that bad.

Answer

It may be time to review the calibrations then. Something has changed that is causing this.

Reply

How can that be done? Putting a new custom program on the truck? Do you think that getting that bad of gas mileage sounds like there might be something wrong or should i just accept it?

Answer

How do you drive? Are you aggressive? With that much power and something lifted as you have it, I know I would drive very aggressive. Also do you do much highway or is it mostly city driving?

Reply

Mostly highway. I dont drive too aggressive cause i know it just complicates my gas problem. When driving on the highway around 60-70mph the truck will go from about 2.5 rpm's to like 4-5 real hard with no inputs from me to try and get back up to whatever speed i was driving to drive at.

Info Request

What condition are your tires in? Are they worn, under inflated, over inflated?

Reply

About 10,000 miles on them, great tread still. They are not swampers either, just a toyo all-terrain. They are inflated to the PSI that the tire requires, i just checked this about a week ago.

Answer

OK, Unless we can go back to stock and evaluate the mileage from there, it will be really hard to know what and where to chase. Also we are at a point that we would need a scan tool to see what all the readings from the sensors are.

Reply

Where/how would you suggest i go about fixing this? Should I try to have a custom program put on it?

Accepted Answer

I think a custom programming would be the place to start with the mods you have done to this truck. Just for the heck of it, can you post a picture of your ride?

Reply

Thank you sir and I will post a picture shortly.

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Question

Optional Information

Year: 2005Make: HummerModel: H2Engine: Vortec Supercharger/Volant Cold Air In-Take Already Tried: Cleaned the air filter, normal maintenance (regular oil changes etc)

Info Request

Welcome. Did you recalibrate the speedometer for the larger tires?

Reply

Answer

OK, the mileage is likely because you are truly traveling farther than the odometer reads so the mileage is not as bad as you think. You will want a custom programming that will fix all these together. Try THIS site.

Reply

That may be true, but when i map quest the mileage to my destination I am filling up about every 170 miles. I'm just having a terrible time believing that i am only getting 170 miles to the tank. I know that when i first lifted the truck it was no where near that bad.

Answer

It may be time to review the calibrations then. Something has changed that is causing this.

Reply

How can that be done? Putting a new custom program on the truck? Do you think that getting that bad of gas mileage sounds like there might be something wrong or should i just accept it?

Answer

How do you drive? Are you aggressive? With that much power and something lifted as you have it, I know I would drive very aggressive. Also do you do much highway or is it mostly city driving?

Reply

Mostly highway. I dont drive too aggressive cause i know it just complicates my gas problem. When driving on the highway around 60-70mph the truck will go from about 2.5 rpm's to like 4-5 real hard with no inputs from me to try and get back up to whatever speed i was driving to drive at.

Info Request

What condition are your tires in? Are they worn, under inflated, over inflated?

Reply

About 10,000 miles on them, great tread still. They are not swampers either, just a toyo all-terrain. They are inflated to the PSI that the tire requires, i just checked this about a week ago.

Answer

OK, Unless we can go back to stock and evaluate the mileage from there, it will be really hard to know what and where to chase. Also we are at a point that we would need a scan tool to see what all the readings from the sensors are.

Reply

Where/how would you suggest i go about fixing this? Should I try to have a custom program put on it?

Accepted Answer

I think a custom programming would be the place to start with the mods you have done to this truck. Just for the heck of it, can you post a picture of your ride?

Reply

Thank you sir and I will post a picture shortly.

Related Car Questions

Year: 2005
Make: Hummer
Model: H2
Engine: Vortec Supercharger/Volant Cold Air In-Take

Already Tried:
Cleaned the air filter, normal maintenance (regular oil changes etc)