If only you knew what you were talking about and then I might believe you. But you are clearly delusional here.
After 155,000 miles it’s not using any significant amount of oil so do you honestly believe it’s just going to become a massive oil burner all of a sudden? After 22 years on this board it still amazes me how many people there are like you who just don’t understand how it all works
OK I'll quit being snarky for a minute. Serious mode: I've been watching and concerned with oil for decades, lurked BITOG for decades, etc. Like you, I thought everything was fine, believed the thin oil is fine mantra that was everywhere, figured that people who knew better than me knew what was up, including on this board. Just went with mfr viscosity recommendations, good name brand synthetic, good filter. 5k changes.
Then a year or two ago Porsche bumped up their recommended viscosity for former 40wt cars to 50wt. Hmmmm. So I took a deep dive. Deep. Turns out the trend to thin *modern* oil is for very slight mpg improvement only. Only. That's the reason. There is no other reason. It does not improve engine wear, it worsens it in almost all cases. Period. (exception living in the Arctic). Sometimes that wear is tolerable. Sometimes not. Depends on what you want. Maybe you want that extra half mpg, and don't care if your engine is an oil burner pretty soon.
I'm not that way, I want my engine to last as long as possible, especially on my old Jeeps, and old Porsche, that they simply don't make any more and never will. I don't want a computer on wheels powered by an engine any more. I hate computer on wheels cars. I have had many. I still have computer on wheels for long trips, but I hate it, and even the computer on wheels I bumped up a grade. I'm sad I didn't figure this out years ago. I want my engines to last forever because I'm completely done buying new cars. They all suck.
With the current crop of oils, thicker is almost always more protective, in general, to a point, so I use as thick an oil as I can reasonably find good data points for. Would I put 50wt in a Honda 4cyl? Probably not, unless tracking it. There's not enough data out there regarding 50wt and Honda 4cyls to make a good decision. But would I bump up a grade to 30? Instantly. 40? Probably not, again, not enough data. But no way would I run 20wt, knowing what I know now. Enjoy your 20wt oil. Maybe you're trading it in soon, maybe you don't care about having to start checking the dipstick at every fill up soon because the extra 1/2mpg is worth it to you. I have no idea.
Like I said, I thought just like you until recently.