I can't speak to the impact on FE when it comes to changing rims and rubber but I can say this. The best thing I did was replace my stock HCH tires with only 2000 miles on them. They are just terrible. I bought quality Yokahama (sp) tires and LOVE them. Better ride, MUCH better breaking and MUCH better handling. Do yourself a favor, add $400 to the purchase price of the car and go directly from your dealership to the nearest quality tire store. I inflate to 40 pounds and get 40MPG in driving that is mostly city.