In Malaysia, usually the mechanic of garage will tell you that, Fully synthetic oil = 10k km semi = 7k km, normal oil = 5k km. Is this true? I heard that fully synthetic oil can go up to 20k km before the next change.
In the USA, we don't use the metric system. We change synthetic oil at 10,000 miles. That's equivalent to 16,000 km. My car had 70,000mi/110,000 km when I bought it, and I have driven it an additional 110,000mi/175,000 km since I bought it, for a total of 180,000mi/285,000km. The engine still runs fine.
I use regular oil in my car and change it every 5,000 miles or 8,000 KM along with the filter. I have over 100,000 miles on my engine and it works just fine. So I don't think that you need to pay over 50.00 for synthetic oil every 16,000 miles when you can pay less than 20.00 for regular oil and filter every 5000 miles. By changing the oil you also are changing the filter and that can and does get allot of dirt and debris in it so changing it sooner is, to me, a better idea.
The real issue isn't the oil "wearing out." It's the exhausting of additives and the accumulation of dirt, debris, and metal particles - all of which will vary with driving conditions. The primary issues is the loss of additives.
Synthetic can go much longer than conventional oils , because synthetic oils have no wax , at all Where as conventional does have wax , yes , the wax that candles are made of , parafin wax , petroleum based Also the molecule is much harder to break down , if at all in synthetic oil It really comes down to your OIL FILTER Thats really why you change the oil , if you run synthetic oil