Abstract: In this paper, the high temperature oxidation experiment of Russian-made 50-1-4? aviation lubricating oil was carried out according to ASTM D4636 standard method. The color redness problem of lubricating oil due to oxidation was investigated by an innovative extracting method with aqueous methanol solution and gas chromatography-mass spectrometry (GC-MS). The chromogenic substances were analyzed. The results showed that the antioxidant T531 was the key factor causing the color redness of the 50-1-4? aviation lubricating oil. The chromophores mainly included the antioxidants themselves and the complex derivatives, such as 1-acetyl-3-(6-methyl-3-pyridinyl) -pyrazoline, dibutyl phthalate, and dialkyl phthalate. It is proved that the aqueous methanol solution has an excellent effect on the extraction and enrichment of chromogenic materials in ester oil.

Key words: aviation lubricating oil, extraction and enrichment, oxidation, chromogenic substance