Can I get better gas mileage with FFV or ?

[07SilveradoNewbie]

Hi - OK so call me stupid and get it over with now...
I just got a 07 Silverado 5.3 FFV (no I did not buy it for the FFV - thank God!) but I am wondering if I can squeeze any better mileage out of this truck? I know this is were stupid comes into play - better mileage on a truck, yeah I know.
So back to my question...I read somewhere that putting a new chip into the truck and changing the compression settings to a higher setting would increase better performance using E85. Does anyone know this to be true, have any information more on the "fact" side of things.

Also, has anyone played around with mixing fuels, gas and e85, maybe 3/1?

Thanks - any information is appreciated