Mitsubishi 4n15 Engine what is normal what is not?

[Dr.Kamiya]

In a tropical climate the winter rating doesn't really mean much. That's the viscosity of the oil at 0°F, which irrelevant because our ambient temp is almost never below 80°F.

Rather than focusing on the 5W or 0W, the second number is much more important for us as it represents the oil's resistance to thinning at higher temperatures. If the car is losing oil instead of replacing 5W with 10W, IMO change from xW-30 to xW-40, or even xW-50.

[dr. d]

i read from an auto journalist,

in today's modern engines with very small tolerances,
the winter rating isn't so much for lubrication at cold temperatures (we are a tropical country here), as it is for the ability of the oil to easily pass thru the very small oil passages in the engine.