"...the 15 inch [steel]
"...the 15 inch [steel] wheels and aero covers actually save fuel compared to the available 16” alloys one can opt for." Can anyone explain this to me? I've always heard that alloys are lighter, so would give better mileage. I note that my 2005 Prius has alloy wheels. If this wheel/cover combination saves fuel, why wouldn't Toyota at least offer the option on the Prius? If it's the aero wheel covers, why not design aero wheel covers for the Prius alloy wheels?