Originally Posted By: PimTac
I'm not a science major but doing 5 minutes of research on the web regarding molecular sounds, I read that you need fine instruments. These are not something the human ear can pick up.
Let's not derail the thread further. The OP has a serious issue and we should concentrate on solving that. I still say swap the filter. Nothing will be wasted as he can save the Ultra since it has less than 100 miles on it. If a engine starts knocking right after a oil change, that is what I would suspect first. There is too much coincidence here.
Again, I'm not talking about molecular sound -- if there is such a thing and, in fact,
there isn't. Sound is propagated through a media. The molecules in the media and the structure of these molecules affect how the sound is propagated. It's just like you don't expect wood and steel to propagate the sound in the same manner.
One of the claims of
this patent (link) is that the use of a VII in an oil reduces the noise. I'm not saying that this is entirely the reason why a fresh oil sounds differently than a used oil but it could be one of the reasons.
We don't know if the OP has a major issue. He describes it as a "
slight bottom-end knock", which could be anything, and it goes away after a while. A quality oil filter like Fram Ultra shouldn't be an issue and there is really nothing in it to be defective to cause engine knocking. It's not an ADBV issue as he said. But then if he's really worried, he can temporarily replace it with a cheap oil filter and see what happens and then put it back.