Ive got a ECSB 5.3 with mods listed below and stock 3.42's and was thinking about getting 3.73's and was wondering how much my MPG would change if any. Right now i get about 12.5 in the city and 16-17 on the highway. Also if I did change gears then should I get a locker also?

 

You will probably not even notice a difference in mileage. I would do a good posi unit when I did the gear swap. Where you start noticing some mileage loss is with a stall.

 

wtf, how is your driving habits? I get about 12.5 city

 

Where do i find out what gears i have? I dont even know. lol

 

What size tire do you run?

What speed do you normally cruise at?

How much of your driving is freeway and how much stop and go (i.e. 60% freeway/40% stop and go)?

 

I don't understand how guys get such bad gas mileage...unless you have large tires then it makes since.

 

I get 16.1 MPG in mine runnin 22's and driving alot in the city. I probably get 18-20 on the highway.

 

on my truck, a 2001 ecsb with a 5.3, and 20" SS wheels, i got about 16ish in town, and 22-23 highway, with a 3.42. I swapped in a 3.73, my in town went up just a fuzz, (maybe .5 mpg) and the highway dropped about 1 mpg.

 

look in your glove box, there should be a code
GU6=3.42
GT4=3.73
GT5=4.10 and a G80 indicates a locking Diff.

 

Supercharger + 6.0 + Stall + Factory 20's + Lead foot = Bad mileage.

Although for a 500hp 5750lb truck 15 avg city/highway isn't bad