Tire Pressure from Dealer @ 50 Lbs ????

In many ways you are right. Pay attention to tire wear patterns and ride comfort.

 

I've been driving it that way for around five days. I thought it felt fine. Maybe a little stiff, but I prefer that to a mushy ride.

 

You have the Tire information section in Chapter 9 Vehicle specifications of your 2016 Prius Owner's Manual, and it should be consistent with the placard on your car's door wall. This is the suggestion from your car maker -- here by TOYOTA.
The max tire pressure on your tire's sidewall is from your tire maker, but it is not the recommended pressure.
Let's see some guidelines from a tire maker -- here by Michelin.
Air Pressure: what should I know?

I think the car maker and the tire maker are quailfied enough to answer this question.
But in actual practice, your could raise the pressure a bit higher than your car maker's suggestion, for better MPG.

 

So some plots from an obscure paper found on the net many years ago:


Lessons learned:

• higher pressure equals lower rolling drag
• on the low-side, it is not linear

A technique used at race tracks is to measure the tire temperature to detect alignment, toe and camber, early enough to adjust and reduce rolling drag. So using an IR thermometer, I fully inflated the tires; ran a 7-8 mile run at 70 mph; stopped on exit and; quickly measured the tread temperatures. Then I reduce the tire pressure ~5 psi and repeated to generate this plot:

Lessons learned:

• Lower pressure leads to hotter tire treads
• Higher pressure minimizes alignment issues
• Higher speeds also leads to hotter tire treads

Speed also has an effect:

Lessons learned:

• 100 km/h ~= 62 mph :: excellent high speed for distance speed
  
• 60 mph = 1 mile/minute
• 120 km/h ~= 75 mph :: USA frequently posted Interstate speed

Above a critical speed, tire vibrations begin to create rolling drag. These vibrations flex the rubber leading to more heat and drag.

One more suggestion is BEFORE rotating tires, measure the individual tread depth of all four tires. This will provide a direct measure of how good/bad the wheel alignment has been:


Bob Wilson

 

More grist:
(1) Around 2008 I had a Subaru Outback with Nokia All Seasons that I ran at max sidewall, 51psi, measured with an Accu-Gage. One summer morning I checked the pressure (51 all around) and later drove in 90F temps about 60 miles at 50-55mph on the interstate to do a TV thing involving the effect of non-hypermiling vs hypermiling using the same car. For the first part the tires needed to be at door jamb pressure, which as I recall was 30?psi, then for the second part pumped back up as I normally have them. I needed to know the pressure after the tires were warmed up so I would know how high to go when I raised the pressure back up after the first part. I was shocked to discover that they were all at 51psi pre-bleeding!! The only causes I could think of were (a) tires with more air in them flex less and therefore heat up less and (b) driving gently means less distortion and therefore heat into the tires due to braking and turning???
Any of you can try this for yourselves, it's so easy to do.

(2) If the OP's tires were at 50psi after driving, perhaps they were too low when he took delivery and heated up to 50psi due to excessive flexing?? The best way to be sure is to measure them when cold, which usually means first thing in the morning after the car has been standing all night.

(3) Based on my experience running at sidewall and above, the more-wear-in-the-center-of-the-tread at higher tire pressures seems to be a myth for modern radials. I ran the OEM Bridgestone Potenzas on my Insight-I for 60,000 miles at 65psi (sidewall 44psi) and the wear was pretty even across the treads (digital tire gauge), if anything LESS wear in the middles than at the edges. At that point the tires were NOT worn out; I replaced them mainly because that size was used solely for the Insight-I and I was worried it might not be available in the future. And I ran the OEM Goodyear Fuel Assurance tires on my 2011 Prius for 50,000 at sidewall pressure (44psi). When I sold the car, all four tires were just under 5/32" DEAD EVEN across the treads (wear bars are at 2/32", so not quite worn out yet - OK for summer use at least).

To me higher pressures seem to be about more than just a rolling resistance reduction. If they reduce rolling resistance to the point that the car can run engine-off in EV or coasting in more situations, the fuel saving is magnified beyond just reducing the rolling resistance.

I suspect that raising the tire pressure in a modern radial simply decreases the bulge in the sidewalls, especially at the contact patch, because the sidewalls are more flexible than the treads are?