I have been running our 2016 C-Max (with the Energy Saving Michelins) at 50 psi. The max is 51 (for a reason). I called and talked to Michelin and they said it was fine if I was OK with the 'ride'. I recently bought a used 2017 (now we have 2 of them) and the selling dealer had to tires at 36-37 psi. My wife and I drove both cars home (50+ miles) at the same speed on the same road. I got 35 mpg. She got 45 mpg. When I got home I pumped the new C-Max to 50 psi and now I'm in the mid 40s mpg.
The tire sticker does not know what tires you have on your car. How can it? Just check the sidewall of the tires on your car and trust what the manufacturer of the tires says.
The ride at 50 psi is very close to what it feels like at 35 psi in my opinion (see experiment above). My wife doesn't like a rough ride but she's fine with the way things feel on our 50 psi C-Max.
Paul - can you chime in there?
pressures are up where they have been high 30's to 40... Mpg getting better. been a light winter, have been very careful about heater use. so maybe my initial reports of the crappy milage were a bit premature.