Jennifer Love Hewitt pumps gas into her Mercedes

For nearly three years, California drivers have been shelling out an estimated $3 billion more annually for gasoline than researchers think they should be spending. The problem is, no one knows exactly why. The Golden State regularly ranks in the top three for retail gasoline prices in the nation, typically falling just below Hawaii and tying with Alaska, where prices are, on average, 60 cents higher than the rest of the nation, according to AAA. And, on Wednesday, California drivers will …