Updated

Retail gas prices plunged an average of 23 cents nationwide in the past two weeks, marking a return to pre-Hurricane Katrina (search) levels, according to a survey.

The weighted average price for all three grades declined to $2.45 a gallon on Friday, said Trilby Lundberg, who publishes the semimonthly Lundberg Survey (search) of 7,000 gas stations around the country.

Self-serve regular averaged $2.43 a gallon nationwide. The price for midgrade was $2.53, while premium-grade hit $2.63.

The average pump price for all three grades on Aug. 29, the day Katrina made landfall on the Gulf Coast (search), was $2.65, according to the survey.

The lowest average price in the nation for regular unleaded among the stations surveyed was $2.06 a gallon in Tulsa, Okla. The highest was $2.74 in Miami.