Motor group AAA reports U.S. drivers paid, on average, $3.75 for a gallon of regular unleaded gasoline Tuesday, up 15 cents compared to the same time last week.
A series of refinery outages, a switch to more expensive summer blends of gasoline and higher oil prices are also behind the price increase.
Mark Griffin, president of the Michigan Petroleum Association, told the Detroit Free Press that spring price fluctuations are normal but usually not this early.
"This year it seems to be a couple of weeks early," he said. "And what drives most of it is speculation; the oil markets start speculating that the demand is going to come and that drives (prices) up."
Michigan has some of the highest gasoline prices in the country. Though down about a penny from Monday at $3.90 per gallon, Michigan prices are up 10 cents compared to last week.
"The cost of gas is irrefutably affected by rampant speculation in the oil market," DeLauro said in a statement.
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