Folks,

Do the math.  Calculate your savings (10%? 15%?) over a year, and decide if
it's worth it.  Probably not, since you can save as much by slowing down, or
even with a product like this:  www.ca40g.com  (I have no interest in this
company, but I've tried it and it did work for about a 10% improvement in my
Scion xB  (30 to 33 MPG hiway over 10 tank fulls).  I'd be curious to see
what you folks find if you try it. I'm going to try it in my EVC this
summer.  It's a bit of a PITA to deal with though, its an oil based liquid.

People swap out the WBX for more power and reliability, not economy.  It
takes the same amount of power to move the heavy, un-aerodynamic Vanagon
Regardless of what engine is in it, so a slightly more efficient engine will
give you slightly more mileage.

Put in a diesel if you really want economy, and you'll have the best of both
worlds--you'll be forced to drive slower ;-), and you'll get terrific
(relatively speaking) mileage!

Stuart