The average price of a gallon of self-serve regular gasoline in Riverside County fell Friday to $4.22, marking its lowest level since June 28, 2021. The price declined by 1.7 cents from the previous day, according to figures from the AAA and the Oil Price Information Service.Gas prices in the county have dropped on 31 of the past 32 days, falling a total of 47.9 cents over that period. This includes a 1.8-cent decrease on Thursday. After declining for 20 consecutive days, prices rose slightly by one-tenth of a cent on Dec. 8 before resuming their downward trend the following day.Compared with recent benchmarks, the average price is now 10.9 cents lower than one week ago and 45.8 cents lower than one month ago. It is also 3.2 cents below the price recorded one year ago. Since reaching a record high of $6.373 per gallon on Oct. 5, 2022, Riverside County gas prices have dropped by $2.153.Doug Shupe, corporate communications manager for the Automobile Club of Southern California,…..