sorry to hi-jack this tread!! but i also run 87 octane..maybe thats the problem??? i'll give some 93 a try...

 

when my 2500 6.0 was stock it got 11.5 to 12.2 mpg...i got a 93 tune from allen ( along with a cai and magnaflow cat back)and went to 14.5 to 15.5...its all in the tq mgmt in the 80e trans..delete some of that tm and your mpg will go up...

 

thats sounds like exactly what I need to do!!! but I will say I absoluty love the truck other than the mileage I guess i need to get used to it..

 

i get around 13-16 in my 5.3..mixed drivin.

 

yea..5.3's get alot better mpg than the 6.0's

 

My 03' 6.0L 2500HD got 11-12.5 average stock. Since lifting/gearing/supercharging etc... the average is 9.7mpg, best I see is at 55mph, 13-15mpg. 65 mph = 11 mpg, anything over 75 and it's below 10mpg. With my gearing 4.88's & 35's (about equal to stock tires and 4.10's) I see 3,000 rpm at 80 and about 9 mpg, don't cruise much faster than that for long periods and if I keep it below 75 I can get over 10 mpg. Gas milage goes down really bad when towing or in town. The 6.0L is thirsty, in the heavy HD's. I found (before supercharging) that the gas milage was always better on higher grade gas. Now it just sucks all the time and I can't even run the cheap stuff at all, but it is much funner to drive

 

Bet that wouldn't be as big of a gap if we could compare them in the same chassis. I think it's more a weight and drivetrain efficiency thing than it is the motors, the 6.0L isn't much better than the 8.1L in the 2500 chassis. Throw a 1000 lbs in the bed of a half ton 5.3L and see if it still does better.

Anybody have a stock n/a 6.0L in a half ton? What kinda milage do you get?

 

In my parents 03 LQ9 Escalade they get 15.7 I think. Is your truck 4wd? I would say 10-16 depending on how you drive it. Also if you haven't already pic up some e-fans they supposedly help alot.

 

When I got my 99' w/ 62K bone stock and 265s running 3.73 I would get around 17mpg. Now after my 285(heavy tires) and a custom tune I'm getting about 15.5.

 

all good info. thanks.

[QUOTE=BeefTip]You must stay in the gas all of the time(nothing wrong with that of course ) QUOTE]


you could say that!! lol. i have a beater that i drive almost all the time, unless it is nice out, or im in the mood to tear somethign up. i get those mpg on the highway too. i have a problem with leaving the pedel in one place when i drive.

how about the guys that did motor swaps.

my truck is ecsb z71. anyone swap in something close to that.