The annual AAA cost of vehicle ownership is out and it's readily available from their website.
This year's averages are somewhat higher than last. The composite cost per mile average for driving 10,000 per year climbed from 62.1¢ per mile in 2007 to 71¢ per mile in the 2008 report.
Not surprisingly gasoline was the major change from the previous year - from $2.56 per gallon to $2.94 per gallon. Maintenance costs actually went down for all sizes of vehicles. The calculations assume a 5 year ownership with 75,000 miles with the vehicle financed at 6%. Although this finance assumption somewhat overstates the cost of ownership for many people, the AAA numbers are nevertheless a consistent and useful reference. Carsharing companies citing these numbers may want to include a charge for parking, as well.
According to AAA, when they first published the summary in 1950, gasoline cost 27¢ per gallon and driving a car 10,000 miles cost 9¢ per mile.