CAMARILLO, Calif. (CNN) -- Gas prices plunged nearly 14 cents over the past two weeks to a national average of $2.18 a gallon of self-serve regular, a survey said Sunday.
That's a drop of 13.62 cents from the prior two weeks in the latest the survey of about 5,000 gas stations nationwide, said Trilby Lundberg, publisher of the "Lundberg Survey."
A $4.32 drop in the price per barrel of West Texas Intermediate crude was responsible for nearly all of the decrease, she said.
The U.S. benchmark closed Friday at $51.99 per barrel, equivalent to a 10.3-cent-per-gallon drop, she said.
The drop nearly cancels out the 13.88-cent increase in the cost per gallon of gasoline that occurred between Nov. 3, 2006 and Jan. 5, 2007, said Lundberg.
Lundberg cited soft demand for home heating oil due to mild winter weather and the failure of OPEC to comply with its November pledge to slash production for the price drop.
But she predicted any further price reductions would be smaller, if they occur at all, in coming weeks. "It's unlikely we will see price drops of this magnitude in the near future," she said. "I'm not sure it's bottomed out, but the bulk of the price drop has already occurred."
The average self-serve regular prices fell below $2 in six large cities -- Tulsa, Okla.; St. Louis; Wichita, Kahn.; Louisville, KY.; Minneapolis; Jackson, Miss.; and Detroit, which had the nation's lowest prices -- $1.86 a gallon.
Honolulu drivers paid the most, at $2.81 per gallon. Here are prices in a few other locations:
-- San Francisco: $2.62
-- Long Island, N.Y.: $2.44
-- Boise, Idaho: $2.26
-- Chicago: $2.25
-- Boston: $2.25
-- Houston: $2.07
-- Atlanta: $2.03
The last time prices fell so much during a two-week period occurred between last Sept. 22 and Oct. 6, when prices tumbled 14.5 cents.
Sunday's price is is nearly 15 cents below what it was a year ago. 
