Why shake oil bottle before use?

[Eiron]

What about striation of components? Is this something that can happen to the various additives in the oil? Or even to the oil itself?

I guess I'm just thinking about all the oil I've got in the garage & how long it's going to take me to get thru it (ten year shelf life, eh? hmmm ... might be close ...). If all the best, tasty bits (moly or whatever) end up along the bottom & lower sides of the bottle, then shouldn't I "re-blend" those ingredients rather than throw'em away?

Also, what about VOAs? If the additive pkg has natural "settling tendencies," shouldn't I shake it up before I pour out a sample & mail it off? Wouldn't that give me the closest "as intended" analysis?

 

[Mystic]

In a good quality motor oil, it seems to me that no chemical additive should settle out of the oil. If I was using a motor oil brand where chemical additives were settling out of the oil, I think I would find another motor oil to use.

Possibly, chemical additives might setle out if a quart of motor oil had been sitting on a bench for severla years, especially after the oil has started to change in chemical composition. But an oil that has been sitting on a bench for ten years is not one that you would want to use in your engine. It would no longer meet specs, and it would probably eventually go bad.

Junk that people sometimes put into oil (like PTFE) that do not belong in oil might settle out. Just another reason not to use such stuff in the first place.