Which Add Pack Ingredient = Dispersant?

[LoneRanger]

Which ingredients in an oil's additive pkg help it disperse or spread out on surfaces, i.e. capillary action, etc.?

I was wondering because I have a bottle of Elf Excellium DID 5W40 diesel oil that even though I keep wiping sides of the bottle off, oil keeps sweating down the sides from the cap neck, even though it was poured weeks ago. I know, wipe off the neck good and it'll stop, but I have a bottle of Mobil Clean 5000 5W30 also with a little residual oil around the neck and it doesn't sweat down the side of the bottle nearly as much. I'm thinking the Elf oil has more/better dispersant in the additive package (?).

Actually sort of a contest I was letting happen-- which one would sweat down to the bottom of the bottle first. Elf is the clear winner.

 

[JHZR2]

dispersants as additives provide for the dispersion, i.e. the prevention of agglomeration of fine particles. It is a particle surface modification.

The oil spreading this is just nature trying to go to its lowest energy state... The syn oil obviously does this better... or else youre seeing it diffuse through the bottle, which i doubt.

 

[chevrofreak]

I've noticed that just about every synthetic oil I've used will have oil running down the side of the bottle next time I pick it up, but I've never had it happen with a conventional oil.

 

[FrankN4]

Zinc, Calcium, Sodium, Magnesium, to name some that show up on inexpensive V/UOA's.

 

[oilyriser]

We could start trying the "plastic repellancy test" on all our oils...

Yes, some do bead up on plastic and won't run down. Some even bead up a bit on metal. It must have to do with surface tension.

 

[Tom NJ]

Dispersancy is not the same as creeping. What you are observing is most likely due to differences in surface tension.

Tom NJ

 

[LoneRanger]

So then wouldn't we want the oil to have a low surface tension so it spreads and creeps and keeps a film in bearings and on parts when the engine is not running? That is, we would want an oil that does not 'bead up' on surfaces?

 

[Tom NJ]

Creep is not necessarily good as it can spread oil from surfaces that need lubrication to surfaces that don't need lubrication, and the oil could varnish on such surfaces if they are hot. That doesn't mean it is bad either - the effects are probably too small to matter. Oil is adequately supplied to needed surfaces through mechanical means, and the SAE & OEMs have not seen a need to set surface tension specifications for motor oils.

Tom NJ

 

[berlyn]

Hi LoneRanger,
same with Redline race oil..

 

[oilyriser]

It would be good for corrosion protection if the oil got all over everything. Maybe this feature is important for boat motors, or backup generators that are stored outside.

 

[JAG]

I don't think there is any modern reputable motor oil that will leave dry spots inside an engine. Some oils are more prone to creeping on surfaces. Adhesion forces (oil attracted to surfaces) fight against cohesive forces (oil trying to minimize its volume). Oil in a vacuum with little gravity present or if its in orbit will become a sphere due to cohesive forces minimizing its volume. Viscosity comes into play by resisting the oils motion...internal friction.

About 7 years ago I put a drop of Red Line 10W-30 and Valvoline Synpower 10W-30 on a steel plate and heated it up slightly. The Red Line spread out over a larger area than the Synpower did. I concluded it was due to Red Line having greater adhesive forces with the steel. The esters are polar and the steel has some polarity (maybe the wrong word for a solid) too.