I like it, I really want 18's though, how much better mileage?
Don't know yet, just got them installed two days ago. According the "industry" I've seen things published like 3% and 4% improvements using LRR and fuel efficient tires. But here's some statistical numbers that I do know. Comparing the 235-45/17 Pirelli P6 to the 225-50/17 Khumo ecowing:
Rev per miles went from 821 down to 805.
Rotational mass was reduced 3lbs per wheel. P6's were 25lbs (one spec said 26.4lbs) and the Khumo's are 22lbs.
Compared to the stock 16" Hankook
Rev per miles went from 836 down to 805!
Rotational mass unchanged as the hankook and khumos weigh the same.
And as best I could find the stock 16" mambo wheels and the 17" akiros wheels also weigh the same. shown as 23-25lbs. But that's an assumption from searching the web.