How do I choose between all these viscosity options?

It was noted here a long time ago that cars in the U.S. spec thinner oils for CAFE standards while the same car and engine in Europe will spec a heavier oil and longer OCI.
Not sure about longer OCIs ... I mean USA car OMs are calling out 10K+ mile OCIs for engines specing 0W-16 and xW-20. Heavier oil outside the USA because the engineers are not tied-down by CAFE and spec thicker oils to give more engine wear protection.
 
 
The last time I was regularly changing my own oil, I owned 1998 and 2003 Hondas. I then moved from the US to Australia, bought 2012 and 2016 Hondas, and no longer had a garage, so I've had the oil changed by my mechanic. Now I have a garage again and it's time for some oil changes, so I pulled out my owner's manuals and found something surprising: my recollection is that my older Hondas recommended one oil weight for cold conditions, and one for warmer ones. My new ones recommend from 1 to 4 possible weights across three different temperature ranges. For example, this is from my 2012 Honda Jazz (Fit) manual:

-30 to +40C: 0W-30, 0W-40, 5W-30, 5W-40
-20 to +40C: 10W-30, 10W-40
-15 to +40C: 15W-40

The manual itself gives no indication of how I would choose between these, other than the operating temperature conditions. Needless to say, where I live in Australia the lowest winter temperature might be 0C on a couple of days, which suggests that I could choose any of these 7 weights of oil! My mechanic used 5W-30 at the last change. The car has 166k kms on it, I've only owned it for 2 years and have no prior service records. So: what else should I take into consideration here, when choosing an oil weight?
Sounds like lots of common sense going on "down under". Different oils for different temperature 🌡️ ranges. I like it. These cars/engines are similar to everywhere else, so in theory they took should have the same choices I would think. Tell us which one you picked.
 
Sounds like lots of common sense going on "down under". Different oils for different temperature 🌡️ ranges. I like it. These cars/engines are similar to everywhere else, so in theory they took should have the same choices I would think. Tell us which one you picked.
I went with 10W-30. I don't know if there's any reason to try a -40 next time. Maybe a good idea since the car is over 100k miles, and I have a suspicion that it may have been thrashed a bit before I got it. I haven't done a compression test though.
 
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