. revenues from sales of non-petroleum merchandise through these retail outlets totaled $ 2838 million in 2008 , $ 2796 million in 2007 and $ 2706 million in 2006 . the demand for gasoline is seasonal in a majority of ssa markets , usually with the highest demand during the summer driving season . profit levels from the sale of merchandise and services tend to be less volatile than profit levels from the retail sale of gasoline and diesel fuel