A while back I replaced the crummy OEM tires on our 2010 Prius with Michelin Energy Saver A/S tires. After driving on them for a while, my unscientific, anecdotal observation is that we are getting at least three or four more MPG with these tires. On our recent 1200 mile field trip, we averaged 53.5 MPG, which is better than we usually get on a road trip. I don't think we've had a tank less than 50 MPG since we got them.

The "low rolling resistance" Energy Saver A/S (as in "all season" and not to be confused with the regular Energy Saver "summer" tire) rides well (as new tires usually do), handles well, and has good traction and braking on wet roads. They are more energy efficient at the expense of slightly less tread life.

I had a little trouble locating them (partly because of confusion over A/S v. non-A/S version) but Stevenson Tire in Maryville got them in for me overnight and I was out the door by about 10:00 AM the next morning. I paid about $10 more total for nitrogen, which is mostly a gimmick but theoretically helps prevent leakage for more consistent tire pressure.