Retail gas prices have continued to drop across the country, falling an additional 11 cents in the past two weeks, according to a survey released Sunday.

The weighted average price for all three grades dropped to $2.16 a gallon on Dec. 2, said Trilby Lundberg, who publishes the semimonthly Lundberg Survey of 7,000 gas stations around the country.

Self-serve regular averaged $2.13 a gallon nationwide. Midgrade cost $2.24, and the price for premium was $2.33.

Prices have fallen about 88 cents a gallon since September, Lundberg said.

Among stations surveyed, the lowest average price in the country for regular unleaded was $1.89 a gallon in Tulsa, Okla. The highest price was $2.55 in Honolulu.