best LQ4 gas mileage upgrads

[themb2g]

I will be installing a 2007 6.0 lq4 and 2004 4l65e. I am putting it into a 72 blazer. Basically i am trying to find some cheap upgrades to raise the gas mileage as much as possible. Has anyone done any mods to a set up like this and can recommend something?

Thanks.

[ls1nova71]

That's an easy one, don't put a 6.0 in it. Not to discourage you, but find a 5.3, it'll get better mileage and power will only be slightly down. Where 6.0's really shine is they have the potential to make huge power, but they're not real easy on the gas. If you were building something that you were going to take to the track and try to knock down 10 second quarter mile times, then it would be a great start. However if you're building something to cruise around in, a 5.3 would be a better choice in my opinion. When people see it, most will not know the difference anyway. You can sell the 6.0 and buy a 5.3 and have money left over too, to buy other parts for your swap. I've personally had both, and have been doing LS swaps for over 10 years, and this is just my honest opinion.

But to answer your question, a set of headers, a good quality live tune set up for economy, and a really light right foot would all help. But from personal experience, that last one is hard to find while driving a truck with a 6.0!

[TR65]

Them

I have been driving LS motors since the first ones in Vettes. My current 6.2LS3 gets an honest 21-22 mpg driving back and forth to work.

My 6.0 LS2 in my 65 C10 gets an honest 16-17 driving the same route. The difference seems to be aerodynamics. The truck has twice the frontal area and twice the drag coefficient I believe.

The key to good mileage with the big LS motors is to get the RPMs down. They have plenty of torque to run very low RPMs cruising. Both of these vehicles run 1800 rpm at 70 mph in high gear.

TR

[jayssunm]

Originally Posted by TR65

Them

I have been driving LS motors since the first ones in Vettes. My current 6.2LS3 gets an honest 21-22 mpg driving back and forth to work.

My 6.0 LS2 in my 65 C10 gets an honest 16-17 driving the same route. The difference seems to be aerodynamics. The truck has twice the frontal area and twice the drag coefficient I believe.

The key to good mileage with the big LS motors is to get the RPMs down. They have plenty of torque to run very low RPMs cruising. Both of these vehicles run 1800 rpm at 70 mph in high gear.

TR

My dream MPG! Going to pull my 67 out of storage and start working on it in 2013 after I find a new job. More pleasant to drive is #1 on my list. Gas mileage falls into this list. Not sure an LS motor is in my budget, but the 6 mpg I currently get isn't either!

[shrunken66stroker]

Let it breath. Free-flowing intake and exhaust will help a little with gas milage, but that's the obvious stuff. It sounds like you're set with what engine and trans you're dropping in so the only other way to get the rpm's down, as TR suggested, is to put some highway gears in the rear end. Then shed as much weight as possible and if it's a 4X4 think about getting the least aggressive tires that will still take you where you want to go. And one more thing, keep your foot out of it. Good luck.

[themb2g]

Thanks everyone. I have been picking out new exhaust and intake as well as a tuner.

[TR65]

Just some more info.

The tires, the aero, and the inertia losses all together account for only about 30% of the fuel use. Knock each down by 10% and you would only increase mileage by 3%. Actually I think our trucks have considerably more aero losses than the numbers used for modern cars.

Anyway, most of the losses come from thermodynamics, pumping losses, engine friction losses, transmission/diff friction losses, and accessories (P/S, AC, Alt ...). All of these losses are reduced by lowering the rpms. Every cylinder has to fire every two turns of the crank and it takes fuel to fire.

Here is a rough distribution of where the fuel goes.

TR

[shrunken66stroker]

After reading TR's chart I realize I forgot to mention throwing away the mechanical fan and replacing it with an electric one. Great breakdown TR. And yes, our trucks are as aerodynamic as a barn.

[Super73]

An electric fan and transmission tuning picked my wifes Trailblazer SS up 3mpg on the freeway and a little over 1mpg on average mixed driving. In other words, put an electric fan on it and lock the verter at low throttles. Lock it in 2nd through 4rth gear and shift it early!!

[TR65]

Right guys! Running a mechanical fan is just pouring gas on the ground. My electric fan doesn't even ever run unless I idle for 5 minutes.

Another point about tires. It is very difficult to make small diameter tires with low rolling resistance. Tire rolling resistance goes down as 1/(tire diameter). Doesn't mean you can't make low rolling resistance small diameter tires but you are fighting physics to do it. So for best mileage get a high quality (= $$) large diameter tire, as light as you can find. I don't think the increase in inertia losses will be important.

TR

[TR65]

You know the sellers claim 1 mpg from adding a tonneau cover. I put one on but I didn't get a good base line on mileage before. I think it did improve mileage about 1 mpg. The drag from an open bed is pretty high.

TR

[STOCKISH]

Put a block of wood under the pedal! The 6.0 is so fun to drive it's hard to stay out of them. Last time I changed my K&N filter it had a footprint in it from stomping on it all the time!

[BR3W CITY]

Idk, I get around 16 on a 6L truck with too much cam, a power-sucking trans, and big tires on a 12bolt.... I don't think I can squeeze better than that.