A survey says the average price of a gallon of regular gasoline in the U.S. has fallen 4 cents over the last three weeks to $3.67.  Industry analyst Trilby Lundberg said Sunday that crude oil prices fell over news that Libyan output has risen and Iraq’s production was not substantially harmed by recent violence.  Diesel averaged $3.94 a gallon.  A year ago, the average was at $3.50 per gallon as it was still going down.  The average price for a gallon of regular gas in Illinois is at $3.75, down 12 cents from 2 weeks ago.  Of cities surveyed in the continental U.S., Tulsa, Oklahoma, had the lowest average price at $3.35 a gallon.  San Francisco had the highest average at $4.12 a gallon.