I've been wondering is there anything about the new generation Gm 6.0 liter that might make it understandably terrible on fuel? I understand that the 2011 Hd trucks are heavy but is there anything that could be done motor wise to make them more efficent ? Do the heads in stock form flow poorly? I could maybe understand the mileage if the performance of the stock truck was better but still seems underpowered even with a tune. I haven't done anything else to the truck but a tune from blackbear. I was hoping maybe when the aftermarket caught up an exhaust,cai,new tune and possibly a supercharger to make up some of what i feel is and underpowered truck. Is there anyone who might be able to shed some light on this subject. I understand this is something of a subjective subject but any gearheads out here that would comment on this would be greatly appreciated. The truck is a 2011 2500 Hd 4x4 eclb with 2500 miles on it. Thanks

 

its not a performance truck, yet that is, usually a tune will wake one up pretty good, its a big heavy truck too, all come into play

 

If this is a brand new truck your 6.0 should be the ly6 with L92 heads and vvt. Try a simple intake tube/dry filter and a free flowing exhaust and a tune. Don't forget your in a 3ton truck too.

 

My post is long, but try and read it and not just skim it please

Get used to it is all I can and will ever say. Why? The heads don't flow poorly, they flow overly well. Much to well to make an efficient 364 cid truck engine. The L92's have huge ports that flow in excess of 300 cfm on the intake side. That's a great thing if you want an engine that can spin to 7500 rpm and make like 650 hp........ but wait we have engines that are rev limited to 5600 rpm and make only 360 HP...... Too much isn't always a good thing and you are seeing why. What makes a great performance cylinder head on a Corvette does not equal great truck engine. You have a peaky wannabe high revving 6 liter in a truck that is way too heavy for it and depending on your gears legal to tug 13000 lbs.

Ever notice that your 6 liter kinda turns on at around 3500-4000 rpm and then of course has to shift right away? That's the cylinder heads for you in a nutshell. When you have such a small displacement engine breathing through a large port intake velocity will slow down. It's not rocket science, it's simple flow dynamics. Now the engine has to actually work harder to get the same air charge into the combustion chamber at low rpm. They try and offset the effect by advancing the cam at low rpm and coming up with a transmission that has a 4.02:1 first gear. It's all to compensate for the lack of low end power that the engines produce and try and get them revved up in their powerband faster.

What does that equal in the real world? A turd at low speed that struggles to move. I drive an 09 2500HD extended cab standard bed 4X4 with an LY6 and it's not really any fun to drive at all. You can tune and add all the bolt on junk in the world but you won't fix the engines characteristics........ Well unless you want to add about 100 cubic inches or maybe put on a set of smaller port cylinder heads. My truck lives with around 1000 lbs of tools on it, a canopy and a roof rack and it's mileage too is poorer than my old LQ4 truck plus it really struggles unless it's matted........ Which also attributes to the poor fuel economy lol. I run a 31" tall Goodyear Duratrac on my truck as I run lots of poor lease roads and so forth. Yours are worse with heavier at least 18" rims ( mine has the fugly 16" PYO's on it) and a 32.5" tall tire adding to unsprung weight you have to spin.

The LY6/ L96 would be much better suited in a performance truck that's light. Not in a heavy duty 2500 or 3500. They could have continued on with the LQ4 and did better than this, they have more low end power even with the free flowing 317 cathedrals they have. Any good builder will tell you that L92's are too large and simply overkill on a 6 liter engine. Then GM turns around and bolts them on themsleves on a "truck" engine. Well you daily drive the results and I am sure you can figure out that the good builders out there aren't all clueless. The application demanding low end power even makes this combination more ridiculous because now by design the torque is shifted even higher in the curve before it comes in with any authority so to speak.

The L92's are wicked heads, don't get me wrong as I may go that route on my 94's LQ9. But that's a sub 4000 lb 2wd destined for the strip with a big convertor and lots of cam..... not a loaded 8500 lb work truck.

 

Driving habits are what kills gas mileage. Plain and simple.

 

Yeah, driving habits kill fuel mileage, but a truck that is by nature a turd is kind of the anti-hypermiler. I drive GMT900 2500HDs almost every day at work, both stock and on oversized (285/75-16 or 285/70-17) mud tires, both on and off pavement, and I can tell you that I often need to put my foot down a lot more firmly than I did in the 800 6.0 HDs or in my 1500 6.2.

 

My work truck is a 2008 3500 hd chassis cab with an 11' stahl work box on the back.

I hate to admit it but it is a slow heavy turd that is in passing gear all the time just to get moving.

The 6.0's are awesome engines, just not in a heavy truck.

All HD trucks should have a diesel period.

 

I wish I would have read this before I purchased mine. I had a 2005 2500hd 6.0 with no complaints. My 2011 is a total turd! It really makes for a long day driving this around. I will be trading it for a dmax! I should have driven one before buying it, I can't believe how much difference there is. ps-no driving habits can change the way this poorly runs, and it's a gas hog! 8.0mpg

 

anyone actually try to trade in a semi new truck with 2500 miles on it? What could the trade be worth? Maybe the DMax is the way to go instead of modding the 6.0l I'm contemplating the trade?

 

Could I cahnge the heads to something smaller to balance out the engine? Which ones? I have read about the patriot 243 but i really don't know what to look for in a set of heads. thanks to all again