What I did was use those plastic page holders you use in 3-ring binders but taped it to the inside of my window. Now I can slide in whatever message I want, especially when I'm updating my MPG.
And I also used the Thoreau methodology of simplify, simplify, simplify:
left side window: (I can't see well if its on my right rear side window)
40+
mpg
ecomodder window cling (next to it)
rear window:
40+
mpg
Besides relaying information they also make for impromptu sun shades!!!
