That was me~!
I have used 5W-20 motor oil in every vehicle I've ever owned starting with a new Dodge Polara 500 in 1965 with a 383 cu in motor. That first oil was Atlantic Imperial. I've lived in NJ and FL. I've never had an oil related engine failure.
My father drove a 1956 Studebaker Power Hawk powered by a 259 cu in V-8 which he drove for 170,000 miles before trading it. He used 20 wt oil year round changing oil and filter every 10,000 miles. At trade in time he was using 1/2 quart of oil every 5,000 miles, and that usage was diagnosed as being from deteriorated valve seals.
Thinner motor oil flows more easily than thick oil, and moves more quickly to every part of you engine at "cold start". I think that this is a critical consideration since the greatest amount of engine wear occurs at start up.