Homogenized?

Status
Not open for further replies.
Joined
May 30, 2015
Messages
2
Location
NC
Motor oil and transmission oil:

Synthetic oil has a number of additives, and they do not all weigh the same. If the oil has been on the shelf for a long time (say 3 months), do some of the additives settle to the bottom? float to the top? so that the container needs to be shaken before use?

And what about the drums of motor oil at the dealership (and other shops) that sit for long periods - Do the ingredients separate so that you don't get an homogenized mixture of all the additives?
 
Last edited:
It does indeed happen because synthetic oil is so slippery, the heavier ingredients settle to the bottom in time.
 
3 months is nothing. In the absence of humidity, the additives should stay in suspension for 2 to 4 years. Never hurts to shake, but should not be necessary.

A couple of months ago I noticed some of my product in stores that was in bottles we stopped using in 2004 (11 years ago). I exchanged it for new product, but on opening, there was no additive precipitation. Some people don't know about inventory rotation.
 
The additives are generally fully miscible with the base oils, which means that once mixed they should not separate out. The same as, for example, alcohol in water - you don't get a layer of ethanol floating on the top of a bottle of wine!

Some of the stuff in the detergents is not miscible but is held in suspension in the oil. The TBN stuff (calcium carbonate) is dispersed in the oil by the detergent molecules as "micelles" - small particles in the region of a few µm in size. If these micelles are destabilised then they can drop the calcium carbonate as a sediment. They can be destabililsed by a number of things, including water, UV, reactions with other additives etc.

Another cause of drop-out can be additive incompatibilities - two (or more) additives can react together to form an insoluble gel or other substance.

Also a poorly-blended oil might stratify if it hasn't been heated and mixed thoroughly.

In the case of reactions and destabilisation, shaking the oil will not reverse this effect. Shaking can help mix up a poorly blended oil, but if it is badly blended then there's a good chance that what is in your can is not the right ratio of base oils and additives to get the final mix you need.

In summary, a well-blended, well-formulated, well-kept oil should stay together and be suitable for use for years.
 
Status
Not open for further replies.
Back
Top