I use plastic page sleeves (8.5 x 11") taped to the rear side windows and simply slide in pages with my current MPG results. Also double for sun shades and are big enough to be read from distance. For the rear, I cut the plastic sheet in half and put it into the lower right corner to meet vehicle codes. Still the same sign from the side windows but I folded it down to fit into the 8.5 x 5.5" sleeve.
Nobody has approached me on my "42+ mpg" but it sure does get people off my tail faster than when I didn't have them before. Maybe people think it means I only drive at 42 mph???
