California gas prices are plunging from record highs set two weeks ago as refineries come back on line, motorists drive less and the cheaper winter blend of fuel reaches neighborhood filling stations.

That was expected. But here's a surprise -- a pleasant one: Prices may fall an additional 10 to 15 cents a gallon a week through Thanksgiving to about $4 a gallon, and they could drop to $3.75 a gallon or lower before the end of the year.

"I would be ecstatic if gas prices dropped that low," said Laura Keenan, of San Jose, a respiratory therapist who commutes to Castro Valley and who has paid as much as $4.95 a gallon for her 2004 Acura TSX that requires premium gas. "It gets expensive. I miss the days of 99 cents for a gallon of gas."

The statewide average on Tuesday was $4.40 a gallon, down from the single-day record of $4.67 a gallon set Oct. 9. On that day, the California price even topped the average in Hawaii, which almost always has the most expensive gas in the United States. It's now back down below Hawaii -- by 2 cents a gallon.

The national average is also plummeting. Tuesday's price of $3.65 was down a dime from a week ago, the largest seven-day decline since May 2011 and one of the largest since the recession hit in 2008.

Analyst Patrick DeHaan of GasBuddy.com said California prices will drop to $4 a gallon "or even less" by Thanksgiving. Energy watcher Bob van der Valk said independent gas stations will decrease their prices even more quickly, perhaps drifting down to $3.60 by Thanksgiving.

Rotten Robbie stations in the Bay Area were charging $4.59 a gallon two weeks ago -- the highest price the discount chain has ever charged. But a station on Hamilton Avenue near Highway 17 in Campbell was selling regular unleaded for $4.35 on Tuesday.

Supplies statewide and nationwide are up, and that is leading to falling crude oil costs. December delivery was $86.67 a barrel Tuesday, the lowest since July 13 after crude output climbed to the highest level in more than 17 years.

Gasoline prices usually decline in the fall as refiners switch to cheaper fuel blends that cost 15 to 20 cents a gallon less to produce. But a series of refinery and pipeline problems on the West Coast sent supplies plummeting and prices soaring to record levels this month.

Many motorists wonder if the outcome of the presidential election would affect gas costs, but DeHaan -- one of the nation's most accurate forecasters -- isn't buying it.

"It's not magic; it's what is normal," DeHaan said of falling prices this time of year. "Gasoline prices have a similar ride every year. They bottom out near the new year, peak in April or May, drop in June, rise in July-September, and fall in the autumn. A vicious cycle perhaps, but a predictable one.

"And all of that means that gasoline prices follow a trend, and that an election won't make a difference. There's no magic spigot that opens with gasoline before an election. That's absurd, and so is the belief that elections alter gas prices. Let the myth die."

For now, keep an eye on the pump and delay filling up for as long as you can if you want to save a few bucks.

"I sure hope you're right that we see prices below $4 a gallon soon," said motorist Bob Rumsey, of Saratoga. "But I'm not counting on it. My next car is going to be a hybrid."

Contact Gary Richards at 408-920-5335.