Drivers in Honolulu have something to be thankful for. The average price of gas on Oahu dropped below $4 a gallon for regular on Thanksgiving.

The AAA Daily Fuel Gauge report estimated the average price of gas was $3.996 Thursday, about a penny less than Wednesday and about the same as year ago. The price has dropped almost 35 cents from last month.

Statewide, the average price per regular gallon is about $4.08 cents. Gas has dropped about 54 cents since April 11, 2012 when a record price of $4.618 cents was recorded. Gas prices have been above $4 a gallon in Honolulu since February.

“This Thanksgiving week we’ve experienced more price drops at the retail pump which help the budgets of locals and holiday travelers,” said AAA Hawaii Branch Supervisor Cynthia Hall. “Honolulu is a dime less a gallon than last week, and our state average is a nickel less than last year, which is also good news for everyone, too.”

Wailuku had the highest average prices at just under $4.25 a gallon. But that price is five cents cheaper than last year and 27 cents cheaper than last month. Hilo’s gas averages about $4.04 cents a gallon, down five cents from last week and 44 cents from last month.

Nationally, prices in many parts of the country have fallen recently, and AAA says gas prices could end the year lower than where they started.

The national average Thursday was $3.43, down about 44 cents from mid-September although still about 9 cents higher than a year earlier. Gas started the year at $3.28 a gallon. AAA says it should be between $3.10 and $3.30 when 2012 ends.

Still, because the price was so high for so much of the year, Americans are likely to spend a record amount for gas in 2012. Tom Kloza of the Oil Price Information Service estimates that Americans will spend about $483 billion on fuel this year, eclipsing last year’s record of $471 billion. And that’s even as Americans use less gas by taking shorter trips or driving more fuel efficient cars.

The Energy Department estimates that national gas prices will average $3.64 a gallon this year after averaging a record $3.53 a gallon in 2011.

A number of things affect the price of gasoline. It starts with the price of oil, which can be impacted by everything from the strength, or weakness, of the global economy to tensions in the Middle East. That oil is turned into gasoline and other products at refineries. The U.S. has about half the number of refineries it did 30 years ago. When one goes down due to a fire or unplanned maintenance, it can lead to a shortage of gasoline, which sends prices higher.

All of these factors have come into play in a big way this year. That’s why prices haven’t just been high — they’ve been on a roller coaster. There have been four separate swings of at least 40 cents — two higher and two lower.