Sorry if this is a bizarre topic, but... I've taken off my valve cover monthly to check on the possibility of any cleaning going on in my engine. Well, I noticed that when I had a dino HDEO in, the various lubed surfaces felt "sticky." Now, with Pennzoil Platinum in, not so much. Really, I guess you can tell this out of the bottle. Why is there such a difference. Another odd thing I have noticed is differences in pouring them in. Not so much with Pennzoil, but when I was using M1. As you got to the bottom of an M1 quart, the oil would sort of bounce and roll in in tight litle globules while ever time I pour in dino, it just sort of drips or pours in in a more "normal" fashion. Just some odd observations. Is this just a difference in the molecular structures or what? Why would it be noticeable if each oil needs to have the same characteristics in the engine? Why am I asking such bizarre questions at 11:30 on a Saturday night?