Hmmmm very very interesting. I'm a proud owner of a LS2 in my Z28 but you right I'm puzzled as well. Only difference between a LS2 vs a LQ4 is the heads and material of the block. Maybe the compression as well.

 

Better off MPG wise, NO I have never seen a carb out deliver MPG even over a simple throttle body style injection like that 90 had. I am very familiar with carbs I have been rebuilding, tuning them since 1973 so lack of knowledge is not the problem.

 

My 2011 non DOD 6.2 sierra was as good or better on fuel than any 5.3 I had. And WAY more power. Hook a trailer to it though and it'll get thirsty quick. That was still one of my favourite trucks.

4 door 4x4 with just a hyperjunk tuner

 

Hammer, that's not the first time I have heard a non DOD 6.2 do the same on mileage as a 5.3 motor.

Its just kinda weird the 6.0 motors drinks way more gas than a 5.3 but yet the BIGGER 6.2 doesn't. Otherwise I'm not sure where the 6.0 LY6 hold its ground as far as power and gas mileage vs the 6.2 motor....afterall they basically have the same heads just 12 cubic inches difference between the two. Maybe the factory cam and intake has something to do with. Not 100 percent sure about it.

 

Does the 6.2 mentioned have VVT? If so, might explain part of the good mileage...

 

Yeah the heads and compression are the same issue. 243 heads and 317 heads. Flow the same but 243 has 64cc vs 70+cc chambers.

So the LS2 heads ARE the compression change. Even worse if LQ4 has dished pissed-ons.

 

The 6.2 was a great upgrade over the 6.0. Probably shoulda had cathedral ports for torque though...

 

VVT and the 6 speed help. I have a 2003 1500 HD with the 6.0 and it's thirsty.

 

Lol that's one thing with my 5.3's. they either could barely do a burnout or not at all. The 6.2 would roast the tires with ease.

Anothe Thing with the 6.2 is gm has them shifting like 300 rpm before they even hit peak HP

 

You have to look at total work being done, and the efficiency of the engine

Combustion engines are not terribly efficient to begin with. They all fall around, say 50%
All of them. 2.0, 3.0, 4.0, 5.0, 6.0, all very bad at converting gasoline to work.


If I have a car with a 2.0L engine and it weighs 2800lbs, then I switch the engine to a 6.0 and it still weighs 2800lbs, all else equal, then the work required to push it is equal and the economy should also be equal. What we are neglecting to mention is the heavier rotating components inside the 6.0 and it's transmission which will parasitically absorb more energy (so you will need more work) but the different here between 2.0 and 6.0 can be surprising (not much) when we factor in optimal gearing-rpm for a cruise example:

for example if you were comparing the 2.0 version of the car at 75mph you might see that engine vacuum is 9" Hg, rpm is 2800

WHere the 6.0 can cruise at 75mph with 1200rpm and 17" Hg (because the vehicle is so light) If we calculated the difference in parasitic loss between a 2.0@2800rpm with 9" Hg worth of load and a 6.0 @ 1200rpm with 17" Hg worth of load it would be very similar if not in favor of the 6.0. Even at idle condition, the 2.0 needs 900rpm and the 6.0 would need around 500rpm, so factoring in RPM Is a huge economy advantage for engines that can sustain lower rpm with low load (and thus lean air/fuel ratios, small injector on-times).

Couple of real world examples I've seen (cruising around 60-75mph):
stock 2.4L Auto from 1995 - 25mpg @ 2800lbs
Swapped to a 5.7L LS2, 6speed, 4.11gear - 29mpg+ @ 2800lbs
Swapped to a 5.3L Iron, 4l80e, 3.69gear - 25mpg @ 3300lbs~
Swapped to a 5.3L Iron, 4l80e, 4.11gear - 22mpg @ 3300lbs~

A swapped 5.3 / 4l80e with a 3.42:1 gear could probably do 28mpg (looking forward to it)
Injector duty didn't even flinch going from 60mph to 72mph with the 4.11->3.69 gear swap (it went 12mph faster for 'free' because the additional load of the reduced gearing was negligible compared to what them motor/trans needs to turn in terms of fuel)


Its just most of us would rather have the gear ratios for hauling *** than economy.

 

Most 6.0 trucks are low geared, 9.5" rear and 4L80 trans. Lots more parasitic losses there

 

Mind you my 6.2 had 3.73's and a 9.5"

 

Sounds like the 6.2 hauls *** while sipping gas like a 5.3 so you get the best of both worlds. The 6.2 trucks are still pretty pricey though.

Hammer... since you have owned both 5.3 trucks and a 6.2 truck can you elaborate the differences on towing performance, gas mileage while towing, and just overall daily driving of the two setups ?

 

A 6.2 will be as good or better on gas if you drove it nice. Like anything else though if you put your foot into it a lot it'll burn gas.

In my experience a 6.2 will burn more fuel while towing but the quality of the tow is quite superior. No comparison in power

All things considered I probably wouldn't buy another 5.3.

 

my 2000 1500 5.3 has always gotten **** mileage. Maybe mid 14's on a good week all highway. MAYBE. Usually about 13 flat. Now tuned with tires and gears I'm lucky to get 12. I don'tr understand how people are claiming to get low 20's out of the newer trucks when they are still the same, basic, motor. With my commute a 1 mpg increase would net me an extra $400 a year in my pocket. Think about a 6 or 7 mpg improvement. The truck is never getting sold but it sure would be nice to see some better efficiency.

 

We have a 2011 Suburban with a Gen4 5.3/4L60E. Around town it gets about 14-15mpg, highway about 18. The DOD is RARELY, if ever, in 4cyl mode. I honestly don't know why GM bothers with DOD. Waste of time and money. People I know with 1500 pickups usually do a little better; these Subs are heavy! lol

 

Hammer thanks for the response....

Anotherws6 is your truck factory or modified with gears, tires, exhaust etc ?

 

it's tailored to meet government fuel economy testing. That's it. What t gets in the real world doesn't really matter

 

I kinda figured that's what it is. I do know I could do a DOD delete and see NO difference in mileage. But I don't wanna bother with that. It's our main ride and can't go down very long. lol

 

No point in deleting it unless something goes wrong