Oil viscosity - why the 20W-50 BS?

20-50w ...20w when cold and up to 50w when hot 'oil viscocity lowers with heat'

It's about film strength people, the bearing and the rest have an oil film on them from the previous run in ...so how fast the oil flows at start up is not a worry, maybe it was in the 50's though.. ;)

Op, u going on about how you still have over 70psi at a cold start with 10-30 w is laughable, u could run 5w and have that much, its after you run it, run it hard, and for a long time. Try actually driving the car 5 hrs down the freeway and then exit and come to a stop...then peek at the gauge and see how lil oil psi u have compared to 20-50w. See I don't know about the rest of you...but I turn 3-4k rpms going down the freeway with my 340...while it runs cool and has a deep pan the hangs in the breeze...the oil is getting hot.Try drag racing all day, how about road race? If you simply putt around town and hand your own *** over to brand x for fear of speed or breaking something, then I'm sure 10w will suffice for you. The other main thing is bearing clearance, how much clearance do newer 4 bangers have compared to the .0025 or so we have in our v8's?
How about the quality of oil u run in the first place? I don't run over the counter swill, though today's swill I'm sure is fine with exception of zinc content....try a better oil, try to understand the meaning of multi viscosity