This is a very interesting article about why aero hubcaps don't make much of a difference on ICE cars but make a much bigger difference on EVs. If you are able to drive on purely Electric Power during your commute at high speeds on a flat or slightly downhill road or freeway, then the aero hubcaps should make a big difference. I think the aero hubcaps probably make a HUGE difference on Prius Plugins especially for people who use electric propulsion on the highway. IF your ICE is always running at higher speeds then taking off the hubcaps might not be a huge hit to your fuel economy. If you are able to coast on electric power for miles at a time on flat or slightly downhill sections of the freeway, then taking off the aero hubcaps probably reduces your fuel economy by a significant amount. Here's Why Aerodynamic Wheel Covers Don't Come On Every New Car
Wow, you didn't tell me there was going to be math involved. Instead of trying to figure it out. I'll just hide my disappointment that evidently getting Aero Hubcaps isn't going to help me.