I'm almost afraid to mention this.
I had this knock, Sounded like a Valve train rattle / detonation when warmed up at any speed mostly when you put a load on it. Drives me nuts!
I tried several oils, Yamalube was the worst! Amsoils was OK, Mobile One no Different, Lucas no different.
THEN I got the idea to add Lucas Oil Stabilizer, I figured out what they suggested and I took out 14 OZ's or oil and added 13 OZ's of the Lucas Oil stabilizer. Gigantic difference if not a 98% cure.
Now when I am on freeway and I twist the throttle all I hear is mean machine and air sucking in.
Someone else needs to try this and let us know if it works for you.
LUCAS is thick like the old STP SO I suggest you add it directly into the engine in the fill plug on the engine, (If you know where that is) OR just add it to the engine that has been warmed up. Then jump on and mix it up!
Personally I am going back to Amsoil but will use 16 OZ Lucas Oil stabilizer and the rest Amsoil since LUCAS mixes with anything.
BTW I did try the Luca synthetic Oil Stabilizer, That did not produce any results.
Magic touch was 14 OZ Lucas Oil Stabilizer and the rest of the 4 Qt's in Whatever oil you use, I think it will quiet it down no matter what oil you use.
MC