IIRC, there was a stink about MPG ratings around the very early 2000's when toyota claimed 41 for the camry.
I believe everyone started revising theirs down around then.
50 IMO would be very difficult prior to a decade or so ago and even then was in a super small car with a tiny engine- IE honda fit.
My guess was those astonomical clams were at least partially embellished.
My manual 2003 PT got 27 average. Was rated 36 highway.
At the same time, my wife's hyunday elantra got about the same.
She wanted better but after doing extensive research, you had to get a MUCH smaller car at the time to do much better IE 30, which incedentally was the fit.
You're probably tired of hearing it but I'm super happy with my 2015 Renegade 1.4t manual, currently at 33.9 for the past three tanks.
Been very reliable and has a slightly better power to weight ratio then a 318 Duster.
The 8/9 speed automatic only gets 34 highway. about 28 mixed.
Wife currently has a hyundai kona. She's averaging 34, and I can make it get almost 40 if I try (using cruise and a light foot).