We just got a 2012 Civic (manual trans), and it came from the dealer with 40psi in the tires. I was amazed!
It was getting great mileage, but I thought I would try bumping that up to the sidewall max of 44 psi. It didn't improve the mileage any, and doesn't seem to coast any further (no scientific testing, just using on the on-dash fuel meters & speedo), ride is only a tiny bit more harsh than at 40psi but handling is a little worse.
I'm going to switch back to 40 psi.
For more i-VTEC discussion, you might want to try this thread:
http://ecomodder.com/forum/showthrea...tml#post310062