On an annual basis, retail gasoline prices hit an all-time high in 2011. The average price for all grades was $3.576 per gallon, vs $3.299 in 2008.

Meanwhile, the shale gas revolution has set the stage for declining prices per mmbtu of natural gas.

Natural gas spot prices. Source: http://www.eia.gov.

The chart above shows the price of natural gas per million BTU delivered to the Henry Hub, a large pipeline interconnection point in Louisiana. The current ratio of oil price per barrel to gas price per mmbtu is about 33:1 ($100/bbl to $3.00/mmbtu), a historically low value. The energy equivalency is about 6:1.

Transportation and distribution add significantly to the price of gas at the retail level, but even there the gas price is about a 40% discount to oil on the basis of energy content.