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Why 6.0s are so thirsty?

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Old 10-01-2017, 07:16 AM   #1
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Default Why 6.0s are so thirsty?

Just as I asked why is 6.0 motors so THIRSTY compared to a 5.3 and even older motors such as a 454 big block?

Yes I know the 6.0 motors have bigger bores over a basic LM7 5.3 or a ls1 5.7 but they all have the same stroke. Guys with 5.3 motors have claimed as much as 20 on the highway....
A 2007 Chevy 4x4 reg cab long bed 2500 with the 6.0 gets 10-11 mpg in town. On the highway expect 13-14.

Do a bigger bore ALWAYS mean a decrease in miles per gallon?

Could GM did a better designing the cam specs for the 6.0 motors?

Yes I also know the 6.2 motors most of them have DOD which I hear people complain all the time about and they just hates it with a passion.

Let's throw this out for fun... 454 averages 12 mpg around town and 14 mpg highway. The GM crate 502HT barely gets 11 mpg around town and it barely tickles 13 MPG on the highway. The 502HT motors makes over 500 ft lb at 2XXX rpm and have 377 horses to back it up.

Hook a 30ft camper up for a family vacation or your car for the drag strip and things only gets worse for the already thirsty 6.0 motor but pulls a load better than a smaller 5.3 motor.
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Old 10-01-2017, 09:45 AM   #2
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All things being equal, I wasn't aware that certain 6.0 motors were any worse than other LS based motors. My 6.0 LQ9 gets about the same gas mileage as 5.7 LS1 with basically the same top end and same bolt on mods
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Old 10-01-2017, 09:53 AM   #3
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Gas mileage??

A thirsty motor is good. Feed that girl lol. Powah!!

Not a negative post.
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Old 10-01-2017, 09:58 AM   #4
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Might be the rear axle ratio. 6.0 tend to be used more for pulling or hauling.
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Old 10-01-2017, 09:59 AM   #5
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Quote:
Guys with 5.3 motors have claimed as much as 20 on the highway....
A 2007 Chevy 4x4 reg cab long bed 2500 with the 6.0 gets 10-11 mpg in town. On the highway expect 13-14.
It's simple physics. A bigger displacement engine will take more fuel, there's no way about it. More air = more fuel = worse fuel economy HD trucks that the 6.0s come in are a bit bigger and heavier thus will take more fuel to run, not to mention the different drivetrain options and differences.

Plus, you can't really compare 1 person's driving habits with someone else's...they can be completely different even in a simple task such as driving on the highway. My dad gets the same kind of mileage on his 4 banger Kia Optima as I get in my 5.7 liter V8. So take those MPG numbers with a grain of salt.
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Old 10-01-2017, 10:09 AM   #6
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Bigger bores typically are less efficient as far as combustion goes.
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Old 10-01-2017, 10:25 AM   #7
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The biggest thing here is that 5.3's are usually found in 1/2 ton trucks with decent rear gears, where 6.0's are in heavier trucks with 3.73 or worse, plus they are working harder pushing a heavier truck around.
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Old 10-01-2017, 10:55 AM   #8
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Quote:
Originally Posted by Tuskyz28 View Post
Just as I asked why is 6.0 motors so THIRSTY compared to a 5.3 and even older motors such as a 454 big block?

I have a 1986 C-30 4-door dually. It had a SM465 4-speed 454 4.10 rear...

I hated that combo towing my race car, or anything else for that matter. Wasn't happy with the power or mileage. I switched to 3.55 gears, still wasn't happy.

I swapped to a 6.0L 4l80e combo. Mileage went from 8-10 towing 14 tops empty. To 14-16 towing...up to 18-19 enpty.

Not a big deal in the grand scheme of things, but almost doubled...
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Old 10-01-2017, 11:06 AM   #9
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Not only a far more efficient engine, but a tranny with overdrive all helped there. You probably lost some torque (those 454's have that! lol), but the 6.0 likely has the same HP or even more, so running empty is still good.
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Old 10-01-2017, 11:27 AM   #10
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Quote:
Originally Posted by CattleAc View Post
I have a 1986 C-30 4-door dually. It had a SM465 4-speed 454 4.10 rear...

I hated that combo towing my race car, or anything else for that matter. Wasn't happy with the power or mileage. I switched to 3.55 gears, still wasn't happy.

I swapped to a 6.0L 4l80e combo. Mileage went from 8-10 towing 14 tops empty. To 14-16 towing...up to 18-19 enpty.

Not a big deal in the grand scheme of things, but almost doubled...
How do you like the 6.0 compared to a 454 big block as far as towing ? How about reliability ?
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Old 10-01-2017, 11:38 AM   #11
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Older BBC's were not fuel sippers my 1990 SS454 1/2 ton would get at best 9-10 mpg on the freeway, drove it from Wi. to Fl. in 1991, 500 bucks in fuel lol, now if your comparing a 1/2 ton with the 5.3 to a 3/4 ton with a 6.0 you have to figure in the added weight and the huge difference in rolling resistance of the heavier drive train and added wind resistance of a truck 3 inches higher, level out a 1/2 ton and add slightly larger tires and you lose 2-3 MPG.
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Old 10-01-2017, 11:41 AM   #12
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Older BBC's were not fuel sippers my 1990 SS454 1/2 ton would get at best 9-10 mpg on the freeway, drove it from Wi. to Fl. in 1991, 500 bucks in fuel lol, now if your comparing a 1/2 ton with the 5.3 to a 3/4 ton with a 6.0 you have to figure in the added weight and the huge difference in rolling resistance of the heavier drive train and added wind resistance of a truck 3 inches higher, level out a 1/2 ton and add slightly larger tires and you lose 2-3 MPG.
I'm quite sure your 90 454 truck was fuel injected ? Do you think it wouldve been better off with a older traditional carb?
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Old 10-01-2017, 11:51 AM   #13
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Quote:
Originally Posted by Tuskyz28 View Post
How do you like the 6.0 compared to a 454 big block as far as towing ? How about reliability ?

Man, I haven't found anything I don't like about the setup I have now over the old combo.

The 454 I replaced had just been installed right before I got the rig. Had about 5000 miles. Leaked oil, burned oil. I'm a hard core, old school big block Chevy guy...I hated that thing. Rarely drove it. The 6.0L LS I installed had 140,000 miles. Dry as a bone, never add a drop between changes. I drive this thing every chance I get now...
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Old 10-01-2017, 02:50 PM   #14
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Bigger bores typically are less efficient as far as combustion goes.
Hmmm... well does the valve size effects combustion? Must I remind the 6.0 motors mostly came with cathedral smaller valve heads vs the LY6 which came out with the large valve and intake ports L92 heads.....
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Old 10-01-2017, 03:34 PM   #15
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I'm quite sure your 90 454 truck was fuel injected ? Do you think it wouldve been better off with a older traditional carb?
No way Tusky. A good injection setup(which the GM ones are) will out-do a carb in power, efficiency, and throttle response any time, given both are set up right to begin with.
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Old 10-01-2017, 05:28 PM   #16
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I have a 2010 2500HD, 4X4, crew cab short bed with 6.0 and 3.73's. Lifetime average mileage on the computer is 12.2 mpg.

I have only beat 12 mpg once, about 13.5 (calculated) on a recent road trip.

I replaced the original 265/70/17's with 295/60/18's and it was more sluggish around town but on the highway rpm's are down a few hundred but there is no real change in mileage.

I don't worry about it much, I just roll on the throttle and have fun.

I may even pay for 4.10's in the future.

I agree that the difference between 2500 and 1500's is mostly due to more displacement in a heavier truck with lower gears.
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Old 10-01-2017, 06:51 PM   #17
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243..... how much gas mileage you get towing a car?
Is you happy with your truck/motor or do you rather have something else?
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Old 10-01-2017, 06:57 PM   #18
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I've puzzled over this myself. I found the LS2 to be great on gas and the LQ4 to be horrible. I chalked it up to poor compression from the 317's.
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Old 10-01-2017, 07:06 PM   #19
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I guess I should add that I run F-body manifolds, dual's, no cats and have good tune on it...I think a lot of the stock LQ4's out there could benefit in the mileage dept with a better tune...
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Old 10-01-2017, 07:15 PM   #20
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CattleAc and Darth hit two important things; tune and compression. I have a feeling that trucks are tuned to run on the rich side to prevent excessive knock with hard running, plus timing a little on the "late" side of things. It would not have to be very rich or very retarded, but a little of each would have its effect. On top of all that, the lower compression does not help things economically either.
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