Continuing our coverage of consumer behavior shifts at petrol stations and convenience stores, the U.S. national average for 87-octane gasoline has remained above the politically sensitive $4-a-gallon level for three weeks. Goldman analysts have released a new note indicating that a majority of convenience stores are seeing drivers buying less fuel and trading down in-store.

Bonnie Herzog, managing director and senior consumer analyst at Goldman, penned a note titled Q1 "Beverage Bytes," which covers a survey of 32,000 retail locations, or about 21% of convenience stores nationwide.

"Despite the improved outlook, it appears that some consumers are already changing their behavior as gas prices remain elevated (at ~$4/gallon). Our retailers are seeing consumers purchasing less fuel, downtrading within the store, and declining basket sizes," Herzog wrote in the note.

More than half of respondents (53%) said they are already seeing changed consumer behavior with gas prices around $4 a gallon, while another 37% expect behavior to shift if prices remain elevated. Only 11% said they have not noticed any change.