PLTL-03 Film Characteristics per MIL-PRF-32033
Lubricating oils may be exposed to elevated temperatures during usage. Thin films of oil are particularly vulnerable to evaporation. If heating of the thin film causes the oil to become tacky, gummy or hard, the oil may not properly protect the system. This test determines changes in thin films of lubricants exposed to elevated temperatures.
A glass panel is coated with a thin oil film of the sample, air cured and then heated as per the method. A “pass” is reported if the film remains oily to the touch. Gumminess, tackiness or hardness of the film is rated as a "fail".