Retail gas prices across the country have dropped nearly 3 cents in the past three weeks, according to a new survey.

The weighted average price for all three grades had dropped to $2.32 a gallon by Friday, said Trilby Lundberg, who publishes the semimonthly Lundberg Survey of 7,000 gas stations around the country.

Self-serve regular averaged $2.30 a gallon nationwide. Mid-grade cost $2.40 a gallon while the price for premium was $2.50.

Gas prices are 39 cents higher than they were last year, Lundberg said Sunday.

Among stations surveyed, the lowest average price in the country for regular unleaded was in Portland, Ore., at $2.07 per gallon. The priciest was $2.78 a gallon in Honolulu.