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Most motor oil tech data sheets list flash point in terms of the COC test. One oil I am interested in is listed in terms of the PMCC test. The flash point of this oil looks low at 204C, but I understand the PMCC test normally gives a much lower flash point than does the COC test. Anybody know what 204C PMCC would convert to in COC? Also is there a conversion factor or equation?
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There is no conversion factor for these Flash Point tests.

The Pensky Marateen Closed Cup test (PMCC) will always give a lower temperatrure because the vapors that are generated during the heating of the lubricant are not exposed to the atmosphere as they are in the Cleveland Open Cup Method (COC). The PMCC test method has a device that encases the cup holding the lubricant and this traps the vapors generated and concentrating them.

Larry Ludwig
Thanks, I should have posted (but didnt, thinking the post was old and would just die out), but I emailed Valvoline Europe about the particular oil and they indicated it should have been COC not PMCC. So it was just a typo on their part. However, your post is informative. I have seen both COC and PMCC listed for certain oils (Chevron site on their base oils) but now I know it was from two different tests. Paul
Flash Point is tested by 2 methods.

1.ASTM D92- Clevland Open Cup Method (COC)
2.ASTM D93- Pensky-Martin Open Cup Method (PMCC)

Generally speaking for Lubricants & mixtures with solvents the Flash Point is determined by ASTM D 93. ASTM D 93 is used for products with flash point > 75 Deg C.

The difference between values of Flash point obtained by the two test methods for the same product may not be more than 5 deg C.

Hussam Adeni

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