Update. I flushed the engine oil with Liquid Moly and I could tell my engine runs a lot smoother. Here is how I did the flush.
1. Drove the car for a few blocks to get it to operate temp
2. Poured 1 can (500 mL) of Liquid Moly and let it idles for 15 minutes. Once in a while rev the engine between 2k and 3k rpm for a minute or so.
3. Drain the oil, remove the filter and empty all the oil in filter
4. Install back old filter and the drain plug.
5. Use cheap oil and filled up all 5-quart jug.
6. Idle the engine for 15 minutes and rev the engine between 2k and 3k rpm a few times in between
7. Drain and remove the filter
8. Fill up with good quality engine oil and filter
9. Done.