Unless you are drastically reducing the weight of your wheel and tire setup, you most likely won't notice a difference. More aerodynamic wheels will improve mileage slightly, but it will be hard to see the difference unless you perform testing. On my Civic, it took wheels that were seven pounds lighter (11lb ea. vs. 18lb ea.), narrower tires, and smooth wheel covers just to get ~2 MPG increase. Switching to a low rolling resistance tire would probably be able to do all of that by itself.
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2013 Toyota Prius C 2 (my car)
2015 Mazda 3 iTouring Hatchback w/ Tech Package (wife's car)
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