Weight is a large factor when comparing the efficiency of different wheels, not just wheel aerodynamic efficiency and tire widths. The weight of the original equipment (OE) 19" wheel and tire combination and the OE 20" wheel and tire are within 1 pound. The 20" set up weighs slightly more (not sure if the weight of the 19" Gemini wheel covers is included in this weight comparison.)
Low rolling resistance (LRR) tires can make a significant difference in rolling efficiency with LRR tires being up to 8% more efficient in my experience. Neither the OE Continental Pro Contact RX tire or the Goodyear Eagle F1 tire are LRR tires.