Hello -
I was also thinking about a "positive" version :
Follow me for great MPG!
Obviously, you are encouraging people to follow you. The grumpy ones would still bypass you, but your "initial virtual contact" with them would be in the vein of "let me help you".
Here is what I currently do :
The letters are not in the GasSavers font because they are reflective (bought 'em in a 99 cent store).
The "A" is a WW II mileage ration. The little toys are probably distracting/disarming too.
CarloSW2