Actually the original size of the civic 8th gen is 205/65/R15 across the world only we have 195/65/15. The fuel economy shouldn't be affected that much, I did 15.5km/l in my 2007 8th gen on the Islamabad to Karachi highway all along in the 205s.
As for the wearing out, I'm not sure about that as for the CC5 coz I just bought them 1 week ago as it all depends on the roads you travel on, how good you take care of the tyres and all from the potholes and how much air you put in them etc.
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