It will tap at idle as the rpm increases it goes away I tried a liqui moly additive today and got it diagnosed he said it was a single lifter tick and to do a oil treatment snd change the oil please advise what else it could be the engine runs butter smooth it won’t even rattle a cup of water on top or the engine. What could it be I always use penzoil platinum and wix or Honda brand oil filters? It’s coming from the back valve train? I’m so confused

 

Unless a mechanic takes off the rear valve cover and takes a look, it's only a guessing game. It could be VCM causing damage to the camshaft or some other valve-train component. It could be carbon deposits causing knocking or some other issue. We are only guessing since car is not in front of us. A real mechanic will take the time to show you what's wrong and what needs to be repaired.