The oft quoted ASTM D6922

Status
Not open for further replies.
Joined
Dec 12, 2002
Messages
43,887
Location
'Stralia
The "lubricant compatibility test" that means that any oil can be mixed with any other.

Worthwhile using the actual name of the test

"Standard Test Method for Determination of Homogeneity and Miscibility in Automotive Engine Oils"

What exactly is the raft of testing ?

Quote:
Visual color determinations and observations are made
on an undiluted test oil specimen, along with six blends of the
same test oil that have been combined with specific reference
oils. The pour point is then determined for the undiluted test oil
specimen and the six blends. The undiluted test oil specimen
and six blends are then allowed to warm to room temperature.
Color determinations and observations are again made on the
undiluted test oil specimen and six blends. The undiluted test
oil specimen and six blends are heated to 232°C, then allowed
to cool to room temperature, and then stored at their pour point
temperatures for 18 to 24 h. The undiluted test oil specimen
and six blends are then allowed to thaw and a series of color
determinations and observations are made as they reach room
temperature. All data are recorded on a report form.


That's it...

It's not a performance standard, nor does it report that oil A, mixed with oil B exceeds, or even meets, any of the standards that either oil meets for approval or on their own.

The pour point (freezer tipping point) is recorded, and is relevant ONLY for the storage of the oil after it's undergone a heating test to 232C (450F), where it's kept for a day...then thawed out to see...if it's still mixed.

It doesn't qualify that the additives work in conjunction with each other, antagonistically with each other...just that they will stay mixed.

What's the test for ?

Quote:
It is important that engine oils from different manufacturers be homogeneous and miscible with each other, because operators of automotive engines often do not have prior knowledge of the manufacturer of the oil that is currently used in their application, and engine failure can occur if oils are combined that do not stay homogeneous and function properly


Anyway, next time you are told that oils are compatible, it means that they are miscible...here's a link to the standard.

http://www.hdutil.com.br/site/arquivos/0 forum yahoo/D 6922 03 _RDY5MJI_.pdf

THE GF6 Committe made this statement when they referred to ASTM D6922

Quote:
Homogeneity and Miscibility, ASTM D6922


Shall remain homogeneous and, when mixed with TMC reference
oils, shall remain miscible.


http://gf-6.com/sites/default/files/03-ILSAC_gf-6b_2-13-14_draft_rev_10.pdf

Note, that's 6 reference oils, and not any two off the shelf oils that you may encounter.
 
The purpose of the temperature and time profile in the test is to accelerate or push any potential chemical reactions/interactions or additive insolubilities/incompatibilities, which would then likely show up in the observations as hazing, clouding, precipitation, color change, pour point change, and/or phase separation. In this sense it goes beyond mere miscibility and may flag potential performance issues.

In the winter of 1980/81 Quaker State used a new type of VI Improver that passed all of the industry standard tests and appeared to be soluble and compatible. After over 1,000 engine failures in the field, however, it was found that a specific temperature profile caused the oil to exhibit a yield stress from the VI Improver and the oil failed to flow back into the hole sucked out by the oil pump, resulting in oil starvation. Because many failures occurred around Sioux Falls, South Dakota, the temperature profile was dubbed the "Sioux Falls Cycle" and was the basis for the Mini Rotary Viscometer (MRV) test that was developed to catch this sort of problem. The MRV is now an important part of the SAE J300 viscosity classification. QS owned up to the problem and paid the claims.

Tom NJ
 
The ASTM test D 6922 only tests for homogeneity and miscibility, it does not promise any additive compatibility and never did.

Compatibility is the term the oil manufacturers have used.
 
Originally Posted By: MolaKule
The ASTM test D 6922 only tests for homogeneity and miscibility, it does not promise any additive compatibility and never did.

Compatibility is the term the oil manufacturers have used.


Molakule, that was the eye opener for me as I read the standard.

Makes a lot of the blending statements here a little of a stretch.
 
Wouldn't Begin to think I can refute molakule, but nothing I've ever read say that the mixing of dissimilar formulation pcmos results in negative outcomes for engine lubrication suitability. I'd be interested to see if there were authoratative experimentally data driven evidence of such.
 
Originally Posted By: ebr1190rx
...nothing I've ever read say that the mixing of dissimilar formulation pcmos results in negative outcomes for engine lubrication suitability.


The lack of field problems may be because oil formulators generally do not release formulations without running ASTM D6922 and/or other in-house tests to confirm their oils will be suitable when mixed with other oils.

In formulating other types of lubricants I have encountered unexpected additive incompatibilities when exposing the oil to high and low temperature cycles. Such temperature cycling was standard procedure before finalizing and releasing a formulation.

Tom NJ
 
Originally Posted by Tom NJ
The purpose of the temperature and time profile in the test is to accelerate or push any potential chemical reactions/interactions or additive insolubilities/incompatibilities, which would then likely show up in the observations as hazing, clouding, precipitation, color change, pour point change, and/or phase separation. In this sense it goes beyond mere miscibility and may flag potential performance issues.

In the winter of 1980/81 Quaker State used a new type of VI Improver that passed all of the industry standard tests and appeared to be soluble and compatible. After over 1,000 engine failures in the field, however, it was found that a specific temperature profile caused the oil to exhibit a yield stress from the VI Improver and the oil failed to flow back into the hole sucked out by the oil pump, resulting in oil starvation. Because many failures occurred around Sioux Falls, South Dakota, the temperature profile was dubbed the "Sioux Falls Cycle" and was the basis for the Mini Rotary Viscometer (MRV) test that was developed to catch this sort of problem. The MRV is now an important part of the SAE J300 viscosity classification. QS owned up to the problem and paid the claims.

Tom NJ



Thats amazing. A friend of mine had a Suburban that was on the engine failure list. I had no idea it was mainly around the Sioux Falls SD area or surrounding areas. I just ran into this thread today from another link regarding the mixing of oils.
 
Status
Not open for further replies.
Back
Top