average national cost per gallon of gas
1 The national average price of gas in December was $2.51 per gallon, which was the lowest monthly average since May 2009. 2  The average in December 2013 was $3.26 per gallon. 3  Consumers this month spent about $215 million per day less on gasoline compared to December 2013. Consumers this month spent about $215 million per day less on gasoline compared to December 2013. 2  Todayâs national average price of gas is $1.06 per gallon less than a year ago. 3  Many drivers are saving $15-$30 every time they go to the gas station compared to a year ago.