extending rear bumper end caps on a 08 liberty
 

I was looking at the 2010 prius where they have redesigned the rear bumper creating a Sharp corner at the trailing edge to direct air away from the rear of the car as well as preventing air turbulence buildup. I was wondering if i could shape a plexiglass and attach it to my bumper end cap to get the same effect.

http://i53.photobucket.com/albums/g5...2008_other.jpg

What do you guys think? worth the time and effort? How much should i extend it?

I don't think it would have to be big to encourage clean separation; check out the youtube video of Bob Lutz showing off the new vs. concept Volt and aero features; it's basically just a ridge on the corner of the bumper.

That said, it would make a bigger difference if you had wheel covers; your open wheel wells are right next to your rear bumper, so it's unlikely that air has reattached by the time the bumper passes.

You would probably be better off with a tiny plexi-extension on the sides/top of the car since air is probably more attached there. Just like a baby-kammback; would have a small effect, but I think it would be more effective in theory than vortex generators.
Welcome to EM! There are a couple other Jeeps on here that have pulled off some impressive MPGs, FastPlastic in particular.
Matt