CAMARILLO, Calif. (AP) — A national survey of gas prices reports that the average cost of U.S. regular grade gas dropped 13 cents per gallon in the last two weeks.

Industry analyst Trilby Lundberg said Sunday that the average for regular grade gas is $2.94 per gallon, while midgrade averages $3.18 and premium $3.34. Retail diesel averages $3.64.

Lundberg said the price has dropped 78 cents per gallon since its peak in May.

She said the drop has been driven by a decrease in the price of crude oil. She forecasts that will come to an end now unless oil prices drop further.

In the Lower 48 states, San Francisco had the highest average price at $3.27 per gallon, while Memphis, Tennessee, had the lowest average at $2.65.