All you guys who have put 6.0's in your 1500's....what kind of gas mileage are you getting? I'm considering swapping out my 4.8 with one & leave the 3.23 gears in.(personal truck) I intentionally eased around the other day in my company 2500 work truck(6.0) keeping the cruise rpm's at 1800, which is about where my personal truck runs. Surprisingly it worked up to 15.9 mpg on the built-in computer. Understand that was only about 50 mph! Normally it's turning 2800 & getting 12 mpg.I would think the 6.0 should get pretty good mileage in front of 3.23's. Anybody doing it?

 

the 3.73s or 4.10s/11s won't hurt you too much more, its all mainly tune and how you drive it.

 

I had a 99, lq4 in a reg cab 2500 with 3.73. I was probably the drive trane combo I've owned with the 4l80e. It would regularly give me 13-14 in town and when I drove 55 on the two lane ( grandpa slow take offs) I could get 18. I love it. It did all of that with out a PCM tune. I think that it would have picked up 2mpg on both with the tune.

The next truck I bought and still have is an 03 1500HD CCSB with the Lq4 in it as well only I have the 4.10's. Before my PCM tune I was 11-12 in town, and 14.5 at 55mph on the two lane. After the tune I am 13 in town (pounding on it all the time) and I can get 17.5 on the two lane. Pretty good over all for steeper gears and a truck that weighs about 6K.

I think the 6.0 in your truck with a great tune and 3.73's should give you the opportunity to get almost 20mpg. Realistically with all that power and how fun it will be you'll be lucky to ave 14-15 cause you'll beat on it so much. Over all you should pick up a lot more power and not lose too much economy if any.

 

I run a LQ9 in my Avalanche.Compare to the stock 5.3L,fuel mileage did not changed.
Plus I have about 70 more HP at the wheels.Best mod that I did so far.

 

I've got an LQ9 with 4.10s and the mileage is pitiful. I drive basically all city/stop and go to my work everyday and I'm getting about 13 mpg. And I drive like an old fart, nothing over 2200 rpms or so.

 

About 10 in the city, 14-15 highway.. 3200 verter and 410's

 

Mine made 19 mpg driving home from the tuner 75 mph interstate driving. But haven't taken an average including any in town driving.

 

MPFD....what rear gears you got? Cruising rpm's at 75 mph?

 

my truck was never completely tuned, but I would average about 18 on the highway (to and from Cali) and about 10-12 in the city, 6.0/4l80e/3.73s, LTs, no cats, intake. cammed with 241 heads

 

I drive hard w/. 5.3 so that'd be me.

motion427, I like seein stuff like your results. What gears?

charcoal03silvy, how u drive has a lot to do w/. any motor.

MPFD, I'd like u to post in here when u have an idea on city MPG. I could take 19 @ 75mph X-way.

Mike, 13 is too low. My imaginary cutoff is 15, maybe 14 at lowest.

John, that's terrible. I think I do a mix, but for sake of this, let's call it city. That means I'd take a -6/ -7 MPG hit. If u call my drivin HWY, ok -2 isn't too bad. It's just me, but no thanks on 4.10s; I won't go more than 3.73.

Those w/. a 6L in a std 1500 have lighter frame than 1500HD, so that counts for something w/. MPG. I get 16-18 in mixed driving on 5.3 in sig. (pre Efans) Hopefully fans will help even a bit. This is just me, I don't want lower than 15 for my style of drivin, & I have a heavy foot. My only reservation to possibly doin 6L swap is MPG. It's not the cost of swap, cause we all want more powa!