The consumption will be about 3% higher with our 19" Razor compared to the base wheel with aero cover. Unfortunately it is „impssible“ to beat a 18" aerowheel with a 19" aerowheel. You would have to appreciate the looks and better handling with 19".
Of course the tire also makes a difference. I use the Michelin Primacy 4 on my car and it is the most efficient tire on the market at the moment.