I'm just wondering how your gas mileage has changed if you went from 5.3L to 5.7L. I have my old LS1 short block in the garage, and am considering freshening it up and putting it in the truck with the stock truck parts. I might upgrade springs and pushrods and put in an 02 Z06 cam that I have as well, but that's mild. So would going from 5.3 to 5.7 with higher compression end up running a little more efficiently since it'll get the heavy pig around a little easier?

 

I don't think you would see much change, if you can keep your foot out of it..

 

The idea is there along with the real potential but like Wilde Racing pointed out, with a fresh rebuild, you'd be more likely to hammer the skinny pedal more often with the ZO6 cam and springs, along with the gains from the displacement and compression bump. IF, and I say if, you can keep the truck below 2000 rpms the whole time and drive like there is a carton of eggs under your gas pedal then I'd bet your fuel efficiency will remain the same, only power will increase. One bennefit I do see right away is the diet you'd put the front end on from the all aluminum block and heads. Cooling would never be an issue either.

If ya got the money, sure, knock yourself out.

 

+1......its gonna depend on your driving habits