Originally Posted By: Garak
How about this, though. If you shake the container to mix in additives that may have fallen out of suspension, you're also mixing in contaminants that have settled out on the shelf, too.
I have heard this argument before, that the stuff that settles could be contaminates. No idea if they are or not.
I usually don't shake the containers, but I do look in the bottom after I pour. If I see anything, I pour a little oil from the next container into the empty one, enough to cover the bottom of the container, and shake that while the current one is going in, then repeat with the rest of the bottles. The last little bit that pours out after shaking in 4-5 other containers is a lot darker than the oil that had come out, but it is a "super" concentrated additive (or contaminate) dose. Maybe I should save all of it, and after a few years, I would have a super strong oil additive oil change.
It would be interesting to see the VOA difference of oil poured without shaking, and then a sample from 5 qts of "residue" boosted oil.
It is funny Pennzoil is mentioned above, they have been one of the ones that pretty much always has some fallout left at the bottom, but I have seen it in Valvoline and Peak as well.
Oddly enough, I have not seen it in Quaker State, but have not had a bunch of that (I have 3 5 qt jugs of it).