For Toyota latest vehicles Toyota full synthetic oil is the best. But according to my knowledge it is not available in Sri Lanka. Best alternative is other brands of full synthetic motor oils(Mobil 1, Castrol, Valvoline etc).According to your service manual you can change the the engine oil & oil filter.Eg-For Aqua 2013 oil grade is 0W-20 and oil change interval is 10,000 miles(because of the roads are dusty in Sri Lanka it is suitable to change oil after 10000km or 1year duration).Also you can save money from using Fully synthetic oil.
Eg- For Toyota Aqua
When you use Toyota Semi synthetic or synthetic blended 0W-20 oil
4L oil can =Rs5500x2=Rs11000
Toyota Oil filter =Rs2500x2=Rs 5000
Total cost =Rs16000
When you use Mobil 1 fully synthetic 0W-20 oil
1L oil can x4(with discount)=Rs8500
Toyota Oil filter =Rs2500
Total cost =Rs11000
According to above calculations you can save Rs 5000
Advantages of Full sunthtic oils
1. Reduced sludge formation
2. Not degradable in higher engine temperatures
3. Protect parts in engine from friction
4. Increased oil change interval and save money