I took the easy route and ran several strips of duct tape across the openings in the grill and saw an immediate 2 mpg or so improvement in the averages per tank. For my most recent tank I folded in my mirrors and drove more ecomodderishly to and from work.
A few days ago I cut out a cardboard belly pan that runs from the bottom of the front bumper cover to the radiator core support. I also covered the gaps/seams in the front around the grill and headlights with some packing tape, much to my wife's chagrin.
I think I may be n track to achieving a 30 mpg per tank average!
