HOUSTON — Looking for an excuse to pack up the car for a road trip this weekend?

Look no further: The average nationwide gasoline price on Friday was the lowest for this point of the year since 2005, according to GasBuddy, a website and smartphone app designed to help drivers find the best deals at the pump.

The immediate cause of the price break was the shock to global oil markets that came when the Energy Department reported this week that domestic inventories of both crude oil and gasoline had surprisingly surged the week before despite heavy driving on the Memorial Day weekend.

Crude oil prices plummeted by more than 5 percent on Wednesday alone, and are near a one-year low at less than $46 a barrel.