Just purchased the Yaris Cross at the Dynamic trim level which comes with 18'' wheels as standard. The trim below the Dynamic is the Design trim which comes with 17'' wheels as standard. The Design has better fuel economy , i think this is down to will size as everything else between the trim levels is the same in regards to specs. So my question is would it be ok to change from 18'' to 17'' wheels on the Dynamic trim level? Thanks guys.