2013 Prius v (lowercase v) 50+mpg

The "engineers" doubtfully had the last input. Virtually forever, car manufacturers used a compromise of air pressures for proper handling versus comfort. That dictate came from back in the day. With both the advances in tire technology, as well as the tendency towards lower profile tires, there's more flexibility today. Many people that would drive a new Prius with tires inflated to 40 psi and higher would find the ride stiff and uncomfortable. Back it off a bit to find the proper ride without compromising too much performance, and there you have it.

I find my own tolerance level to be 38f 36r. I've had them to 40, but our rough roads became intolerable, for me. Move me down to Florida and smoother roads and my guess is 42 would be great. So far, our tires have worn evenly throughout their life, far better than when we always used the manufacturer psi rating, which typically results in uneven wear. Our 2007 Camry Hybrid just got new Yokahama Envigors. We use 35/35 for that car, which is near perfect. Mileage is 38-39 now at the dash, handles and rides extremely well, rolls beautifully. At 32 psi, it feels like someone put an anchor out. The old Yokas were 40k plus, very even wear, we just decided to replace all four because we appreciate new tires and their rain performance.