On some engines, you can safely exchange oil change intervals by using synthetic oil.

But that's only if the engine is designed to take advantage of it. Synthetic oils are NOT meant to extend oil change intervals for motors not built for extended intervals, as so:

Can you go longer between oil changes if you use a synthetic blend or full synthetic motor oil?
Synthetic or synthetic blended oils are not intended to extend oil change intervals. These oils are recommended for use in harder working engines and to assist with gas mileage, not to extend service intervals beyond what the manufacturer recommends.
Valvoline.com > FAQs > Motor Oil Car FAQs > Full-Synthetic Motor Oil

For most engines, the change interval is programmed based on how long it takes not only for the oil to degrade, but for contaminants to accumulate in the oil. Sitting in traffic speeds up the build up of contaminants and the shearing of the oil itself. If you drive in Manila all he time, stick to the "severe use" service interval, 5,000 kms. If you drive outside the city all the time, with mostly highway cruising, you can extend the interva by using synthetic oil.

Either way, you have to keep checking the condition of the oil. Don't rely on the oil lasting the whole 5k... especially if the car is old or stressed (hot traffic).