(CNN) -- A year ago at this time, U.S. gasoline prices averaged $3.97 a gallon. It was the highest average in all of 2012.
But it's a much different story this year, as prices continue to fall.
The average per-gallon cost in the continental United States is now $3.65, 32 cents less than last year's peak, according to Trilby Lundberg, publisher of the Lundberg Survey. That's a 6-cent decrease from two weeks ago and a 15-cent decrease from six weeks ago.
Lundberg attributes most of the latest drop to lower crude oil prices, but she also credits a more plentiful supply.
"More U.S. refineries are gaining access to lower-priced domestic and Canadian oils and passing these benefits on to their marketers and retailers in the form of slashed wholesale gasoline prices," Lundberg said.
Lundberg expects the national per-gallon average to fall a few more cents this week as long as the price of crude doesn't jump.
The Lundberg Survey canvasses about 2,500 filling stations every two weeks. In the latest survey, the cheapest gas was $3.33 a gallon in Billings, Montana. The highest was $4.05 in Chicago.
Average per-gallon prices in other cities:
Charleston, South Carolina: $3.41
Las Vegas: $3.67
Sacramento, California: $3.86