gasoline + v8 = thirsty engine...just the nature of the beast...plus they add all of these alcohols to your fuel which while burning cleaner, robs your fuel of potential BTU's that can be turned into energy. so you have to burn more fuel to get the same energy with the extra alcohol in the fuels...(this is a problem with winter diesel too...they add a ton of methanol to the diesel to prevent gelling, but it robs btu's from the fuel making it take more fuel to do the same work, as a result the average diesel loses 1-5mpg in the winter depending on how cold the area is you are getting fuel from)

I don't get much better in my diesel, (12.5-13.5) but it has its reasons...

among those reasons:
1. lead foot
2. 315/75R16 tires
3. tuned to over 500hp
4. did I mention lead foot?!

before performance mods my truck used to get 17-18mpg with the oversized tires. hell with stock tires and 3.55 gearing I could probably pull off 23-24mpg.

to hell with that crazy talk! if I want better economy, I'll get another VW TDI jetta that gets over 40mpg driving with a lead foot!