(WASHINGTON, September 21, 2015) Today’s national average price for regular unleaded gasoline marks the lowest price for this date since 2004, and prices continue to march lower. The national average has dropped for 35 consecutive days for a total savings of 38 cents per gallon over this span. The national average price of gas in September was $2.34 per gallon, which was the lowest monthly average since February 2015. 2  By comparison, the average price of gas in September 2014 was $3.39 per gallon.