4.8 Vs 5.3 mpg
 

What is the difference in the fuel mileage between the 4.8 and 5.3? I found a place that sells complete change outs, dont know how much yet, and just wondering the difference. I know the 5.3 makes more power but Im more into mileage as i use my truck as my daily driver and I gaurantee the 4.8 makes better power than my carbed 305.

Re: 4.8 Vs 5.3 mpg
 

All the research I did showed that they were pretty darn close to each other...perhaps 1-2 mpg better with the 4.8L IF you were lucky. (most said they were equivocal.)

I was trying to decide between them for a daily driver build and decided on the 5.3L. I think because of what was available at the time, the added power compared to mpg, resell would be better with a 5.3, and I think because a 6.0 upgrade wouldn't need a reprogram because of the same stoke length with the 5.3L (don't quote me on this one)... blah, blah, blah

But, yes, had a 4.8L been presented to me at the time I would have bought it.

Re: 4.8 Vs 5.3 mpg
 

Just go 5.3, mileage difference will be negligible but the difference in power is noticeable. If you want the mileage run it with an o/d trans and a long enough rear gear. Since it needs to have vats and the other misc stuff tuned out when you do the swap, having a tuner use something like HP Tuners and doing a mileage-oriented tune isn't a bad idea.
There are plenty of folks with near stock (and modded) 5.3/od trans combos seeing north of 20-22 and over while locked up on the freeway @ 65

Re: 4.8 Vs 5.3 mpg
 

Outside of this think about ways to reduce the weight of your truck. Is there a pile of junk you never seem to remove from the bed? Switch to aluminum wheels, lower it, fiberglass hood...

Re: 4.8 Vs 5.3 mpg
 

Thanks guys. I will probably just end up going with a 5.3 just because they are easier to come buy. I found a guy with a complete change out 5.3 with 84K miles for $2000.

The bed is clean and I dont think the other stuff is going to make a significant difference in mileage. Maybe a bed cover but other than that I dont think its worth the effort and money for little or no gain in economy. I get 15-16mpg with my carbed 305/700R4 set up and figure Ill get closer to 20mpg when I swap. Need to start making a list of what all I need. Going to try to do it as cheap as possible with the only "custom" parts being the motor mount adaptors.