Interesting chart for inflation adjusted gasoline prices.
http://inflationdata.com/articles/inflation-adjusted-prices/inflation-adjusted-gasoline-prices/
My guess is that, if you also adjust for taxes, the government makes more on gas the any other entity, and boutique blending, artificial restrictions on distribution (see California) whole sale prices of gasoline are historically low.
If you factor in fuel efficiency gains and historical inflation adjusted wage gains the ratio of fuel cost to miles driven has probably never been lower.
As mandated fuel efficiency kicks in, states must raise taxes to keep revenue stable.