Thanks Romio.

First of all, it is extremely unlikely that you have rod knock or a spun bearing if your oil was never empty.

Although 0W-40 should be used, it still shouldn't cause a knock in your engine.

Second, if it is truly knock, then it shouldn't go away at 1000 rpm, it would get worse with your RPMs.

My guess is that what you're hearing is something related to the emissions system.