Good analogy with the sweater and jeans!
Just because you can do it doesn’t make it the best way to do it.
As a kid, I always wondered why so many Russians in my neighborhood would wear sweatpants a sleeveless t-shirt sandals and jewelry around their necks in subfreezing weather for HOURS.
Figured it meant I could get away with ONE hour. My Mom set me pretty much straight:
Dress warm, son. You never know when a girl / woman / lady may be in need of extra warmth. Offer her one of your extra layers.
You'll be fine, she'll appreciate it one way or another, she'll notice your constitution can handle it, and even if she doesn't warm to you personally,
she'll have something nice to say about you to others. Be more prepared than you need to be, if you can.
Moral of that story so far as motor oil goes: 5w30 or 0w30. 0w20 is too close to the margins.
I have a patient who is 94 years old and in pretty good shape for his age.
I was telling him that if he drinks more water it might help his overall health.
His response to me was “ the only water I drink is about this much (he puts his thumb and first finger almost together) in my scotch,
and that’s the only water I have been drinking for the last 40 years”
He is 94, active and in better shape than most 70 year old guys so I don’t know how much difference hydration makes for him - definitely better but worth the effort? Probably not in his situation but that doesn’t mean you should limit water intake to live to be 90.
Another example of how you can do it but it’s not the best strategy for most cases.
If he gets / keeps enough water from his diet, doesn't shed much water to his environment, and doesn't need to detox from anything other than alcohol (which always has some H2O), he doesn't LITERALLY need to drink too much H2O.
Should still drink more, but maybe he drank plenty of H2O prior to the last 40 years, who knows ...
Closest thing I have to a 'religion' as most of you would see it, is chance/likelihood/probability.
If you take the minimum number of chances possible, that's actually the riskiest life strategy in the EXTREME long run, but / so ...
Whatever it is you're gonna do (or not do), improve your odds whenever you can.
As a result most of my friends tend to find me more prepared than they are for contingencies, the unexpected, emergencies, etc.
To quit blathering, again, moral of that story so far as motor oil goes: 5w30 or 0w30.