Let's see - my last 'Van' got 16 miles to a gallon on the road; my current jeep gets as much as 26 mpg. Neighbor has a Dodge Ram 1500 Hemi - his last Dodge got a little over 18 mpg, he claims his current one gets over 22. Granted not a large, nor statistically valid sample but given the increased fuel mileage of most newer vehicles, we are purchasing less fuel for the same miles driven. Less fuel purchased equates to less taxes collected. Now, that said, this holiday season AAA reported higher POV travel numbers for those going 50 miles or more from home than in quite a number of recent, past, years. So that means that we, the American Public, put on more miles hence purchased more fuel but not as much as we would have (given the same prices) several years ago. (I hope that makes sense).
We are fortunate in that my wife's job actually changed (she retired from Ft Riley KS - a 60 mile per day round trip) and now only has to travel 10 miles round trip. So, with her smallish car she was getting 18 to 20 on the road to work each day (3 gallons) now she gets 15 city so less than 1 gallon. Maybe we are fortunate in being an exception but fuel economy on today's cars and small trucks is improving. Next on the list are the larger trucks - I'm not looking forward to those days but look at Ford (and their aluminum body trucks); I foresee the same for the other truck manufacturers as they strive to meet Government MPG rules. HOWEVER, the EPA or CAFE will have to give - my use of diesel has gone UP since these Diesel Particulate Filters came on board. Off my soap box.