5.3 vs 6.0L in gas mileage question

[jbauto]

Ive been debating build a 6.0L but the guy i bought the truck off of good friend was getting 13L/100km with is about 18 MPG

I would like to hit 400hp and call it a day but dont want super shitty gas mileage.

[oleshifty]

I think average on 6.0's is 14-16 range. So I would estimate you're going to lose 3 or 4 right off the bat. 400hp 6.0 vs 400hp 5.3 ..... 6.0 would probably have better mileage, just because you wouldn't need as extreme a cam, etc to make the power.


The gear/stall is going to be a bigger difference then the engine swap. Can't imagine you're going to have a stock stall, with a 3.23 gear behind a 400hp motor.

[02gmcbandit]

my old 2500 got around 18-20 mpg with a hypertech and flowmaster so i probably lost hp lol but he's right on the money, gears and how well your trans and every moves makes a big diff. a crappy trans will rob hp and gas mileage. my 5.3 with 4.11's gets roughly 22 mpg hwy

[jbauto]

I was thinking of doing a LY6 with a small cam , headers, intake and exhaust and a bigger stall. the truck has 3.73 in it im pretty sure its a 2000 Z71 4x4 with the tow package.