I have a buddy with a 2004 GMC 6.0L Auto 4x4 Ext cab 4.10 gears gets 10mpg. He called me to ask if there were any mods that would improve the MPG on his truck. This truck is factory stock. If anyone has any ideas I will pass them on to him. Thanks Kroutman

Tell him to have it towed around j/k. Little things like exhaust, intake or possibly a bed cover are some of the cheaper ways to go. If he has some money to spend, tell him to look into a programable chip from either PCMforless.com, Westers or Nelsons. I have heard people gaining 3 to 4 mpg city with those.

William

Electric Fans vs. belt-driven fan can help a bit. No parasitic loss from the clutch-operated fan can add 2+ mpg and 10 hp.


They are OEM on many '05 trucks but you do have aftermarket options.

-P.

I sold my 6.0 HD for my current duramax and I will tell you all I did on my 6.0 to try and get better mileage..

K&N Cold Air Intake $200
Flowmaster Muffler $125
Tonneau Cover $150
Hypertech Programmer $300
Gibson Headers $400
Throttle Body spacer $65

none of these mods gained me any mileage..I still got no more than 10mpg city and highway. Since the 4L80e tranny is a 4speed.. the rpm's are higher at freeway speeds.

good luck trying to get more mileaage..I wasted too much money trying.

"Since the 4L80e tranny is a 4speed.. the rpm's are higher at freeway speeds"

Higher than what?

The 4L80E's OD gear ratio is .78 and the Allison 1000's is 0.75

DEWFPO

Wouldn't part of it have to do with the Allison being a 5sp and the 4L80E being a 4. Having that extra gear, I think, would help the truck to get going better and the motor wouldn't have to work as hard to get up to speen. Does that make sence?

William

Usually vehicles with more gears get worse mpg because it's one more gear to run the engine up through, but it does help with having power in the right rpm when you need it. On the other hand, the 06 Allison 1000 will have 6 speeds with 2 OD gears so that should definitely get better MPG by about 10% (based on the OD ratios).

DEWFPO

To bad they won't put the Allison behind the 6liter.

William

How does a 6.0 w/ a 5 speed manual compare to an auto?

Anyone know the same thing with the 8.1?

Just trying to figure out what way I want to go in the summer. Diesel would be ideal, but out of reach right now(just graduating.)

Thanks guys.

I've got the 5 speed behind my 6.0. Not bad, but my trans has a gear rattle that is apparently normal.
If you drive in traffic a lot, you may consider the auto. When I'm stuck in stop and go traffic, it gets annoying to shift all the time. Can't be too good for the clutch either.
When my camper is loaded, I love the stick. I have total control and can use the gears to slow the truck on hills.

The Allison behind the 6.0 would be to cool.

DEWFPO

I traded my 2003 6L 5 speed on my 04.5 LLY/Alison. Gas mileage was awful bad, put 2 1/4" flowmaster dual exhaust on it and a Hypertech programmer, 285's, almost broke me on gas, traded and diesel prices went up (hmm). just my .02

What was the MPG on your 6.0 with 5speeds? Thanks guys.

What was the MPG on your 6.0 with 5speeds? Thanks guys.

9.5 loaded with my camper; 13 to 14.5 unloaded commuting. Higher # when I use the freeway, lower # when I use surface streets.

Wow, 10 is even worse then what I get (I run about 12 for my CC SB 6.0 with 4.10's). Perhaps he should take it to the dealer and have them check and see if it's throwing any codes. The MAF or 02 sensor might be having some problems. Fuel pump could be an issue too (along with perhaps a dozen other possibilities).

I know the 6000 is a thirsty engine, but that's a little too thirsty.

I felt like the 4.10 rearend was likely a mileage eater in my truck, but I got nearly the same mileage at high speeds as I did low speeds. I like the 6.0 and have no real complaints about it, but I wouldn't be too quick to say it's better than the 350 Vortec's. I feel like they got better mileage with nearly the same power.

We have 4 6.0's at work. They get between 12 and 13 mpg, two are 4x4 and two are not. Both two wheel trucks usually have at least 1000 pounds in the bed. Like jim said, 10 mpg seems to low, unless you drive it like you stole it!

mine gets 15 empty on thr highway

I have owned two 6.0's, and as briano mentioned earlier, you will never pay for mods in gas savings if that is all you are looking for. If there was an easy fix to mpg, the factory would use it, which would help their CAFE requirements and sell even more trucks!

interesting comments on the rear ends.... I think the 4.10 actually got BETTER mileage than the 3.73's ... my neightbor has th 4.10 with 12-13 in town while I got consistant 10.4 with a 3.73

on the highwy best I ever saw was 15.4 (tailwind:rolleyes:) while the neighbors 4.10 was getting 16 and sometimes 17 same run!!