(Undated) — The national average for a gallon of regular unleaded continues to trend lower. According to this morning’s numbers from GasBuddy.com, the national average is $3.10 a gallon, down twelve cents from a week ago. Here in Illinois, the statewide average is $3.33 a gallon, a seven-cent decline from last Monday. Across the river in Indiana, the statewide average is $3.02 a gallon, nine cents lower than a week ago. Mississippi has the lowest average in the country at $2.65. Meanwhile, California has the highest average at $4.76 a gallon…