Oil pressure question...I promise it's not another "who likes what' thread!

I always thought oil got thinner as it heated, but the higher number grades would thin less. My interpretation:

10W50 when cold is kinda thin to flow at lower temperatures and when warm, thins a little bit so it gets a "50" grade when hot.

10W30 when cold is kinda thin to flow at lower temperature and when when warm, thins quite a bit so it gets a "30" grade when hot.

When I open a fresh can of any oil, whether it is 10W30, straight 30, or 20w50, it pours out slow because it is thick. When I drain hot oil from the crankcase to change it whether it is 10W30, straight 30, or 20W50, it pours out much thinner/faster than when I poured it in fresh/cold. If I had a lab, I could compare hot viscosity of the 30, 40, and 50 grades and would find that although to the naked eye they all appear to flow fast and thin when hot, the higher grades (40,50) actually don't thin down quite so much as the lower grades (20, 30). I don't see that any of the oils increase in viscosity as they are heated.

However, maybe my observations are all wrong, would not be the first time.