csmc711

iTrader: (4)

If everyone claims that the 4.0 bore engine is the more efficient engine over the ls1 5.7 3.9 bore (or whatever it is), then why do people always say "boy, that 6.0 sure does suck down the gas"?

Now, before you go riding my jock, please refrain from throwing out the "cause people always have their foot in it" analogy at me. The 5.7 gets decent mileage and the 6.0 isn't that much bigger, so, being more efficient, it should have either matched that mileage or done better.

Anyone have some 6.0 in car (not truck) city driving mileage figures to throw my way?

93Z2871805

iTrader: (5)

If all things were identical (head flow, stroke, compression, ring material, piston material, etc), you would increase the ring/skirt contact area within the bore and add a heavier piston, mileage would suffer due to frictional losses and adding weight to the rotating assembly (provided there was no real unshrouding effect). It would probably be minor, but would be noticed. Just a theory.

csmc711

iTrader: (4)

Input is extremely appreciated and the theory sounds great on paper. Im my opinion, that is not theory, but fact. Is that enough for the ls1 guys to be okay and then have the 6.0 guys complain about the horrible mileage? Hmmmmm..........

96capricemgr

iTrader: (1)

The 6.0l has a reputation for bad mileage due to displacement because most folks aren't bright enough to consider the heavier 4L80E and 14bolt axle heavier tires etc. behind them in trucks. Once the label gas guzzler is applied no amount of reality will sway people.
The comments about ring friction and piston weight are valid but miniscule compared to the tranny/axle/tire weight added.

Werewolf SS

iTrader: (3)

Agreed with above.

I have 6.0 block (though mine is bored and stroked out to a 408.) and my mileage is roughly 13 mpg city and 19 mpg highway, I'm pretty happy with that considering I'm .65 liters more than the 6.0. And considering a 2004 Silverado with a 6.0 is rated at 13 city and 16 highway, I must be doing something right.

For reference a stock ls1 Camaro with automatic is rated at 15 city and 23 highway.
And I've gone from 305hp to over 500 so only losing 2 mpg in city and 4 on the highway is impressive to me.

csmc711

iTrader: (4)

I have read that 4l80E have less "rotational" mass than a 4l60E, so, that one will have to be put aside for now. What we are left with is:
1) Ring drag/piston weight (though miniscule)
2) 14bolt axle
3) Heavier tires

Now, to be fair, or least semi fair, I met a guy the other day that had a G8 GT that said she sucks it down. To be totally fair, I will not assume it has the same exhaust cam and intake as an LS1. I KNOW the intake is different .




Is that in a truck also?

96capricemgr

iTrader: (1)

Even if the 4L80E has less rotating mass I would bet the parts are larger diameter and the further from center mass is the more work it is to spin.

Tire design itself plays a big part too factory tires especially on "passenger vehicles" as half ton trucks are pretty much treated now are LRR. On my wife's 7th gen Impala she lost 10% fuel economy when we replaced the factory TigerPaws with a Goodyear that actually gripped something.

Betting 2500 trucks don't get as LRR a tire as a half ton.

Bowtie316

iTrader: (1)

The "more efficient" part of the equation only comes into play with head flow increase due to the larger bore, and the increase is only noticed with greater opening of the throttle. There will be little to no increase in efficiency at the cruising throttle positions. What little gains that are there will be eaten up by increased friction and the extra cubic inches.

All things being equal, the 5.7 should ge slightly better fuel economy, and the 6.0 make slightly more power.

LS2 in a corvette with 6 spd gets close to 30 mpg on the highway. It's not the 6.0 thats the problem.

redtan

iTrader: (5)

It's more efficient at making power, not fuel economy. Clearly more displacement takes more fueling thus should theoretically have worse mileage all else being equal.

96capricemgr

iTrader: (1)

Displacement has a LOT less to do with fuel consumption that people believe. Small displacement is great for flawed EPA testing but not so great in the real world.

Bowtie316

iTrader: (1)

The 6.0 in my silverado "sucks the gas", but that's because it's 6500 lbs, has tons of rolling resistance and it geared to pull a trailer. A 5.3, 4.8, 5.7 or 6.2 would all suck the gas in an application like this.

2nd Gen Fl 'bird

iTrader: (13)

This^^^^^ Camaro around 3500 lbs in stock form vesus 6000 plus in a 2500.
Even 1500 PU is heavy so to speak. It will hurt the miles per gallon.

thunderstruck507

iTrader: (18)

I am in process of switching from ls1 to ls2 so I can tell you for sure what MPG difference there is but I doubt it's much more than the variance I already see (18-20mpg highway depending on fuel, conditions, etc).

93Z2871805

iTrader: (5)

If the absolute ONLY change was the bore, no. It would barely be noticed, if at all. I see you want real world results, but as I can't say I've done a truly apples-to-apples swap, I can only speak in theory.

True, and most people do a more aggressive H/C/I, steeper gears, higher stall, etc. when going through with an LS1 to 6.0 swap (as well as adding 88lbs in some cases), which will all have an adverse affect on mileage.

A.R. Shale Targa

iTrader: (2)

coefficient of drag.............
trucks are like a barn door as opposed to a sleek f-body or vette...in the .29-.32 range, Add to that one ton of additional weight as well

BlackDuk98

iTrader: (34)

Like others have said, weight is a big deal. Our cars are 3800# stock. An iron 6.0 is 110# more than the aluminum 5.7 according to the stickies above. I wish I could tell you my numbers, I am still finishing up my 408 but mpg's will never be a factor for me, I am after the power.

I have (2) 2500hd Silverados with 6.0's that pull car trailers, landscaping trailers and plow all winter. I cannot remember the mpg with the truck empty, but with adding a 900# plow on the front and 500# of weight in the bed for traction, running an 8 hour plow run, the trucks gets 9 mpg pretty much all of the time. Same if I am pulling 10k #'s.

The lighter you go the better off you will be. Motor will have less stress of moving you along.

Jontall

I get 24mpg on the highway, 12mpg city with my LS2, but it has 603rwhp. It is the tune and vehicle weight that will determine fuel economy.

csmc711

iTrader: (4)

Since this is going to be my 300k plus daily driver, I didnt want to drop something in that gets 9mpg when I try to go to the beach 3 hours away and such. Just trying to determine that middle line between poser and fuel economy, for me.

Thanks for the input everyone.