sir the myth of oil change is utterly wrong, practiced wrong.
read any owner's manual the base line ( minimum ) oil change is recommended at 5000 kms, and oil change is suggest at 7000 kms. every user manual suggest oil level check & top up before 7000 kms.
sharing Japanese language manual in english speaking tropical locations is gross stupidity done over this forum done by few.
10w-40 / 10w- 30 down south location - or 5W-40 / 5W - 30 up north location in Pakistan
is the best all weather engine oil. That can be used almost in every vehicle without any after thoughts.
Check the Atlas Honda, Indus Toyota & Suzuki websites for OEM recommended oil specs. They are pouring / recommending 2 different oil grades for selection of user across the country.
synthetic or generics the viscosity remains the same while cleaning agent nano particle additives identify the Price of lubricant.
the digit before W signify the ambient outside temperature for cold start., the last 2 digits signify the viscosity of oil at the peak engine temperature.
please do read over internet