[sbierwagen]

It's supposed to run 5W-30 but for the cold months I do 5W-20. After watching the Project Farm metal on metal wear tests of 0W oils, and the fact I'm not running the engine at -20C, I'm not eager to go any lighter: https://www.youtube.com/watch?v=xtSwaF2evTU

[literalAardvark]

Do 0w-30 not Xw-20. The number on the left is cold temperature performance, where cold temperature =not at operating temperature.

The number on the right is in the manual and you only change it when you go to the track.

Atm you're running a lighter oil than your car is designed to use and it's very likely to be a bad idea.

In the video you linked the only oils you can compare in the way he is comparing them are the 0w-20 and the 5w-20.

Later edit: I've watched that and since the tests the oils only at cold temperature it is entirely inconclusive wrt protection at operating temperature.

And cooking test is just dumb. Your oil rarely above operating spec. The only oil exposure to above spec temps is the oil in the top side while the engine is cooking after being stopped, and the oil in the burn chamber which burns and is then filtered out.

If you want to know how your oil is doing collect it after a service interval and send it to be tested.

[jacquesm]

This.

The latter is also useful to check for impending headgasket doom (or cracks) before it is otherwise visible.

[sbierwagen]

Here's the oil analysis from my most recent change: https://bbot.org/etc/oct2022change.png

The cold starts aren't great for driver comfort, but don't seem to have a big effect on engine internals.

[jacquesm]

The problem is that that cold oil is like sludge to pump around but your oil pump will try anyway. The result of that is insane oil pressure until the oil has warmed up enough to flow and that can cause all kinds of issue, from pump failure to cracks in lines. So it really isn't good but it will not show up in your oil analysis until something fails (and likely catastrophically) leaving your engine entirely without lubrication (you should get an immediate oil pressure alarm though when that happens, the sooner you can switch it off after that smaller the chance of damage).

On my car even with the 0W30 in it in winter the oil pressure starts almost at the top of the scale and as the oil warms up it drops, by the time it is warm enough at idle it sits at the lowest point on the scale + 1 unit. If I use the more sluggish summer oil for too long in winter I'll see it peg the needle on the oil pressure meter, and I have no idea how high it really is. So there is a substantial difference between the two, running temp is more or less the same when the engine is well and truly warmed up.

[jacquesm]

Definitely go for the 0W-30 if you're doing cold runs even if it isn't at -20C. I use it myself in the winter on an older engine for very similar reasons. That video is ... questionable ....