My 2018 owners manual only recommends OW-20. Had my first service today! Not losing a thing in any temperature. A good part of old cars specifying much heavier oils is that viscosity quickly deteriorated. That's why 2,000 mile oil changes were commonplace, and some still believe in them. Engines, cooling, oil, and filters are tons better than that now, so using 30W-50 these days costs you big in efficiency.
I'd point out that the cooling system keeps your engine the same temperature no matter the outside temperature.
Kia dealers use bulk oil from Pennzoil I found out today. 5W-30 semisynthetic or base oil is a lot cheaper. Do you suppose that is why they use it?
2018 Kia LX HEV Metal Stream with Advanced Tech