I read somewhere were Exxon Mobile made about 2 cents/gallon profit in 2010, whereas the fed takes 18.4 and 24.4 cents/gallon for gas and diesel respectively, and states vary. For example, Idaho taxes fuel at 25 cents/gallon for gas and diesel.
Here’s an interactive chart of all state and federal gas taxes:
http://www.api.org/oil-and-natural-gas-overview/industry-economics/fuel-taxes/gasoline-tax