Gas mileage Improvements for 6.0 L

FWD101003 · December 31, 2004

Has anyone had luck improving their MPG on their 2500 HD 6.0L?

What modifications can be made to get fuel consumption lowered?

Steve Cornell · December 31, 2004

I have an 04 GMC 2500HD 6.0 \ Auto Ext. Cab.

I have averaged 13.5 over the last 7000 miles, I have seen as high as 15.2 on a tank.

I played with the VaraRam King Cobra intake system and saw better mileage (aboout 1.5 mpg better) and a performance increase.

I've also read of people getting better mileage from exhausts and tunes, but in my opinion it's going to be hard to "break even", if you spend $500 on upgrades and get 1 mpg better with gas @ $1.75 \ gal and go from 13mpg to 14mpg you will save $96.75 every 10,000 miles, so it would take you 51,680 miles just to "break even" on that $500 upgrade.

This thinking is also the reason I bought a 6.0 this time, I had an 04 Duramax \ Allison Crew Cab which was a GREAT truck but I priced it and someone bought it for what I could buy a new one for, I sold my gooseneck car hauler and really no longer needed the extra power and the very best I ever got with my Duramax was 17.9 mpg but mostly averaged 14 - 15 mpg running empty.

I bought the new 04 for $13000 less than I sold my used 03 for.

I've decided I have enough power to do what I need and it's hard to justify spending the extra money on upgrades that may or may not give me better mileage, I also find that running easy on 2 lanes at 45 -50 (I know who wants to do that) I can get 16 -17 mpg but on the interstate with the cruise set at 75 my mileage is 13.5 - 14, yes these numbers are from the DIC but "so far" it has been right on with every fill up.

BTW, if you would be interested in the VaraRam, I have a complete system for sale, I'll post it in the For Sale section.

FWD101003 · December 31, 2004

I am thinking that a smaller gear might get the rpms down and get better mpg's...but still a big investment. The truck has 4.10 gears now ....the engine has plenty of HP and torque to run smaller gears.

Do you know of annyone who has made that modification?

lazer · December 31, 2004

My 02 HD with the 6.0 got 10 miles to the gallon no matter weather I pulled my trailer or not. This new 05 with the 6.0 and the "DIC" says I'm getting 12.5mpg with only 500 miles on it. I'm as happy as a clam. I like the power of the 6.0 and it does exactly what I want. I always thought if you want good gas mileage you buy a compact truck, but than you really don't have a real truck.

Haulin' 8.1 · December 31, 2004

I am thinking that a smaller gear might get the rpms down and get better mpg's...but still a big investment. The truck has 4.10 gears now ....the engine has plenty of HP and torque to run smaller gears.
Do you know of annyone who has made that modification?

<{POST_SNAPBACK}>

Ironically I'm wanting to go in the opposite direction for the same reason. My 8.1 with 3.73's gets crappy mileage, I'm working on the reasons why it's running rich but I also realize that I would do better with 4.10 gears. 90% of my driving is stop and go below 60 MPH. So with 4.10s I would see easyier starting off and get into OD a lot sooner. Many times I'm stuck just under the speed for 5th gear and have to poke along behind everyone else revved up in 4th. I also have 265/75 tires which doesn't help in this situation.

Do you have 4wd, live near Houston and want to trade axles? I'll do all the work at my auto garage for free. Only expense would be having the dealer reset the computers for the gearing change. I'm currently thinking of doing this with salvage yard axles if one will work out a trade for my 3.73 axles and a old suburban I don't need, maybe a few bucks (those suckers are greedy-lol).

Vernon

FWD101003 · December 31, 2004

I am thinking that a smaller gear might get the rpms down and get better mpg's...but still a big investment. The truck has 4.10 gears now ....the engine has plenty of HP and torque to run smaller gears.
Do you know of annyone who has made that modification?

<{POST_SNAPBACK}>

Ironically I'm wanting to go in the opposite direction for the same reason. My 8.1 with 3.73's gets crappy mileage, I'm working on the reasons why it's running rich but I also realize that I would do better with 4.10 gears. 90% of my driving is stop and go below 60 MPH. So with 4.10s I would see easyier starting off and get into OD a lot sooner. Many times I'm stuck just under the speed for 5th gear and have to poke along behind everyone else revved up in 4th. I also have 265/75 tires which doesn't help in this situation.

Do you have 4wd, live near Houston and want to trade axles? I'll do all the work at my auto garage for free. Only expense would be having the dealer reset the computers for the gearing change. I'm currently thinking of doing this with salvage yard axles if one will work out a trade for my 3.73 axles and a old suburban I don't need, maybe a few bucks (those suckers are greedy-lol).

Vernon

<{POST_SNAPBACK}>

FWD101003 · December 31, 2004

Do you have 4wd, live near Houston and want to trade axles? I'll do all the work at my auto garage for free. Only expense would be having the dealer reset the computers for the gearing change. I'm currently thinking of doing this with salvage yard axles if one will work out a trade for my 3.73 axles and a old suburban I don't need, maybe a few bucks (those suckers are greedy-lol).

Vernon

Vernon,

The truck I have is a 2004 2500HD 2WD w/ 4.10 Gear.. I am looking for a rear end to swap out too. If mine was 4WD we would have a deal that could work out.

If you have ran across a 3.73 locking Differential that would be a direct swap, let me know.

lrymal · December 31, 2004

....This new 05 with the 6.0 and the "DIC" says I'm getting 12.5mpg with only 500 miles on it. I'm as happy as a clam. ....
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Similar increase with my 2005 Z71 5.3, about 2 MPG better in town than my '03 and likewise on the freeway, and with a green motor with less than 500 miles. And this is a heavier body, being a crew cab vs. an extended. I actually popped in at 20.3 MPG at 55 mph. Well, ok... I don't regularly do 55, but I just had to know!

The General certainly did something....

Haulin' 8.1 · December 31, 2004

If you have ran across a 3.73 locking Differential that would be a direct swap, let me know.

<{POST_SNAPBACK}>

Use this: www.car-part.com, but like I said GREEDY.

Vernon

Haulin' 8.1 · December 31, 2004

Hmmm, (FWD101003) I was just thinking I might still trade rear axles with you if you're willing and able. It would be much cheaper for me to only have to buy the front diff from the yards. I'm pretty sure my rear is not locking though.

Eh, email me if you're interested, [email protected]

Vernon

EDIT: Mistaken ID

lrymal · December 31, 2004

Hmmm, Irymal I was just thinking I might still trade rear axles with you if you're willing and able. ....
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Heck fire, no! Nobody's touchin' this new truck's bits and pieces.!!!!! Big Luke is sitting on the porch with a shotgun, keeping an eye out.

Haulin' 8.1 · December 31, 2004

Sorry Irymal, I meant to address FWD101003 but looked at the wrong post when trying to see how to spell it. It's gonna be ok, just take two and it'll all go away. HE HE.

Vern

tmaj1865 · December 31, 2004

I'll chime in with my 2 cents about the fuel milage, I found that if I drive faster, around 80mpg rpm around 2500 I see an increase in milage. My truck is an 01 6.0 4x4 4:10 with 265/75 tires. Now in my case it would seen I need to increase my rear gear ratio to a 4:56 to get the rpm in the best fuel consumption range, which I'm not going to do. In FWD1011003 case would'nt it be better to buy taller tires instead of swapping gears, that way if it does'nt work you can always swap back the next time you buy tires??? If anyone has any ideas on the fuel milage thing, chime in.