fully synthetic,semi synthetic and mineral oils

[niky]

It'll depend. You can use oil safely past the change interval, in terms of distance and number of months... but without a way to test the condition of the oil, it's best to err on the side of caution.

The reason to change oil in a certain number of months is that moisture can form inside the oil system, moisture which gets into the oil and dilutes it and lessens its effectiveness. Sludge and varnish can also form over time if the car is parked for long periods of time or spends long periods of time idling in traffic. (at idle, oil only moves slowly through the system).

I've got two cars with a 5k service interval and one with a 10k service interval. The car with the 10k service interval doesn't drink oil or drinks very little of it by 9000-10,000 kilometers.

The cars with the 5k service interval start drinking oil between 4k-6k... whether you use synthetic or not. The tolerances in the engine cause even synthetics to break down long before 10k. Not all 5k interval engines are like this, but you can't just dump expensive oil into the engine and assume you're "safe" because they're synthetics. You still have to check your oil from time to time to be sure you're getting full protection.

[oj88]

Knowing that driving in Metro Manila is considered severe conditions, I follow the 10,000 km or 6 months (whichever comes first) PMS interval. I plan to keep my car for at least 6 years that's why I'd like the engine to last. That and the use of fully-synthetic oil. Nothing but the best for my car.