Knoking sound comes every morning i start my civic

Hummm With those low miles you shouldn't have an engine knock. Is it a deep low engine knock or a light upper engine knock? Stand by the engine and listen while someone starts the car.

I DON'T like 20-50 in a Honda. Put in the required oil 5W30. The engine is so precise that that thick oil won't flow and it causes engine problems. Later engines require 0W-20 oil. Good luck

[quote:0cf276d50e="anwars65"] I think it comes from upper side of the engins. It starts very loudly and then gradually becomes normal after almost 45 seconds
Please advise me about using a sinthetic oil instead of a conventional. I heard that if a car is not used to a sinthetic oil and ultimatly switching to a sinthic oil could damage the engine seals. is it possible?[color=darkblue:0cf276d50e][/color:0cf276d50e][/quote:0cf276d50e]

I would remove the valve cover and do a visual inspection when the engine is cold. Check all the cam towers and see if anything is broken.

Move timing belt back and forth with your finger and see if there is slack. There should be none.

The problem could be a water pump or cam belt tensioner. If the belt breaks you have lost a cyl head. the recommended replacement is at 60K miles.

I feel the noise is cam belt related and it will radiate toward the top of the engine. Don't wait, have the belt repleced if you feel any slack in the timing belt or the teeth look worn or if you haven't replaced it in the last 60K miles.

It may be stretched and a valve is just touching a piston making a knock. Don't run the engine anymore until you have found the problem. Good luck