Hi. I have a Kia Optima 04 2.4 manual, and over 100k. It runs perfectly untill engine started knocking little bit and recently it's getting louder and worse, I have to use premium gas to avoid knocks, but I wish to fix it. Anyone could tell me what should I do? is it timing???
is Engine dying slowly? appreciate all helps and concerns.


My spark plugs are premuim Bosch and sparked about 20k. changed timing belt 30k before and change oil and oil filter on TIME.