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Old 03-26-2006, 06:22 PM   #1
Swampdonkeys
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Fuel Economy

Ok guys I have a 03 GMC 3\4 ton H/D extend cab 4 x 4 with a 6.0 litter gas pot. The problem is, I am making 12 miles to the gallon in the city on the highway and making 14 mpg with today's gas prices. This is killing my pocketbook, what kind of fuel mileage are you guys making, have you done any modifications what can you guys recommend. I have seen different ads on TV about to chips that adjusts your power and fuel mileage. Has anybody you these? Do they work?

I used to have an 81 F250 with a 351W and it made 15 miles per gallon around the city. I thought when I went to a new truck. It would make a little better fuel mileage. Any thoughts. Any suggestions?
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Old 03-26-2006, 08:13 PM   #2
dennislbrooks
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Re: Fuel Economy

well the combination 3/4 ton, 4x4, and 6.0 liter is going to make it hard to get much better gas mileage. Less engine revolutions would help. You probably get the same mileage pulling a trailer or with a load as empty.
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Old 03-27-2006, 10:59 AM   #3
67ChevyRedneck
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Re: Fuel Economy

This is what GM puts on their website for the 6.0L "Standard in 1500HD, 2500HD, and 3500 models, which are not rated for fuel economy." An extended cab 5.3L is rated at 15city 18 highway not loaded. Mine gets a little under 15 city and varies from 17 to 18.5 highway (5.3L 1500 Z71). The only way to get better mileage out of a 6.0L is to buy a different truck. Those numbers sound correct for what you should be getting. You can throw lots of money at it and get maybe a mile or so better with chips and what not. I think the duramax/allison trucks get much better. Sorry, but as you said you have a 6.0L gas pot

Edit: You may be able to find a lot more information here: gm-trucks.com
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Old 03-27-2006, 11:04 AM   #4
dennislbrooks
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Re: Fuel Economy

My 2006 4x4 4800 auto SWB is new but I will try to get you some actual mileage figures --so far it does not appear to be a gas guzzler. I got the 3.42 axles for the extra mpg.
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Old 03-29-2006, 11:43 PM   #5
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Re: Fuel Economy

Quote:
Originally Posted by dennislbrooks
My 2006 4x4 4800 auto SWB is new but I will try to get you some actual mileage figures --so far it does not appear to be a gas guzzler. I got the 3.42 axles for the extra mpg.
My 2000 Z71 4800/5sp manual/3.73 gets about 17-18 town, and has got as good as 21 on the highway. The 4800 engine has a great combination of power and economy IMO. I recently put a set of 33 X 12.50 - 15 tires on it, and I haven't checked mileage with them. I had LT305/70/16 tires which are very similiar in size, so I do expect much ,if any, change in MPG.
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Old 03-31-2006, 09:39 PM   #6
rubrhammer
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Re: Fuel Economy

I have a 2000 5.3 ecsb 2wd and get 18 1/2 to 19 1/2 local stock with amsoil in the engine. I just put in a computer from Wait4me. I'll let you know in a couple of weeks if it helped the mileage.
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Old 04-04-2006, 08:14 AM   #7
Huck
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Re: Fuel Economy

My 2000 (Z71 4x4, ext cab, 5.3, with tow pack) gets 15 mpg around town and as high as 20 highway if you keep it below 70. The trailer tow pack puts in 373 gears which you need for tow but 3.42 would be better for over the road.
Your 6.0 4x4 3/4 ton is typical as board member "BILL" has the same setup with the same results.
I did managed to see a 1-2mpg improvement with a tonnu cover over an empty bed. Removing the tailgate actually dropped my highway mpg 1 mpg. My truck has 150,000 miles on it and is pure stock.
Chipping might help a little but my guess is that the cost of the chip would offset the gas savings for around 5 years!!
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Old 04-05-2006, 11:09 AM   #8
dennislbrooks
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Re: Fuel Economy

you might contact one of the PCM programmers to see if they can squeeze a little more--- I am working with a Sinister performance, LLC out of Indiana --- to get the part throttle shifts at a higher MPH. I have been talking with a Ryan Gick. www.gmtuners.com ---- these guys may work for Delphi who knows
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Old 07-14-2006, 03:34 PM   #9
FXSTCHIEF
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Re: Fuel Economy

I guess this is the price we pay for owning a 6.0L. I have a '05 6.0L HO EXT CAB Silverado with 3.73 gears with about 4000 miles on the odometer.

I was averaging 13.3 mpg until the recent 3000 miles where it has improved to 14.2. This could be because: 1. The engine is broke in or.. 2. My last 3000 miles have been all freeway or.. 3. BOTH. In either case its not fun filling her up with these gas prices.

I do love the truck and wouldn't trade it for nothing... I was wondering about the Hypertech and what it would do to my fuel economy as well.

When I want fuel economy I drive my Harley.
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Old 07-14-2006, 05:49 PM   #10
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Re: Fuel Economy

'06 GMC 2wd swb - 4.8, 5-speed manual, 3.23 locking rear.
I got 18.2-3 my first tank of gas. Mixed about 60/40 freeway/city.
Second tank I got about 18.5 all freeway (70-75mph) but had a bike rack in the reciever with three bikes and a bed full of bags/luggage for a 4 day trip.
I am just getting down to the end of my third tank of gas but haven't been paying attention to what it was when I filled it. I know I filled it up a week ago Tuesday or Wedsnday so I am pretty happy about that!

I put a set of 17" Denali rims on today. I swear the rims and tires are lighter than just the bare 17" steel rims it came with. Hopefully that will make a .0005 mpg difference...
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