How to save 10-20% on auto gas bills?

1 - Just make it mandatory for ALL car manufacturers to install a data screen like you have in the Prius: simple, easy to read, fun. 5-10% saved right there.
2 - As part of getting a driving license, teach new drivers how to SAVE gas while driving. Another 5-10% saved.
TOTAL = 10-20%. It is that easy...