REx Oil weight

Hi! Newbie here. Just bought a 2018 94ah REx and went to the dealership and bought the filter, crush washer and wanted to buy oil, but the dealer wanted to sell me 5w30. I saw several videos in which they were using 0w30, so I just bought Mobil 1 0w30. Manual says nothing, I started the oil change and when I took the cover off the REx I see a sticker that calls for 0w20, but my BMW dealer has no 0w20 BMW oil.
So, as I started the process, I just put the 0w30 until I can figure out what is going on.
How do you find out the right oil to use? Did it change in different years? Any help will be greatly appreciated!

I think on my 2015 the sticker says 05/30. Seems with later years BMW changed the 'recommended' weight for some reason, but I don't think the difference in the oil weight is super critical.

I usually just order the BMW i3 oil change kit from ECS Tuning.

https://www.ecstuning.com/b-genuine-bmw-parts/oil-service-kit/i3rexoskt2/

My wife runs a 2015/6 REx. Main BMW dealer said 5w30, so I use Castrol Edge fully synthetic oil. Takes 2.6 litres.

Looks like there has been 2 changes to the specified oil weight. It started as 5w30, then went to 0w30, then to 0w20. I wish I knew if there was a design change or just a fuel fuel consumption reason for the change