GasBuddy.com says the average price of gas in Illinois dropped 3 cents last week down to $2.24 a gallon. The national average went up 2.7 cents $2.20 a gallon. The average in Decatur is $2.08 per gallon and the lowest price per gallon of gas in Decatur is a $1.98. The lowest price per gallon in Springfield is $1.98 and in Champaign it’s $2.05 a gallon.