It might be nice to show cost or gallons consumed per day. It would really help demonstrate your tip about not driving at all to save gas. Conversely if you took a roadtrip and got great MPGs (all highway) the dollar per day analysis would show you'd actually spent more money as opposed to saving.
I know you've got other shtuff to take care of, but there's my two cents. (which buys less and less gas every day...)