Abstract: For lubricating oil samples containing calcium alkylbenzenesulfonate detergent with different base numbers (referred to as oil sample), the high temperature detergency, water separation and extreme pressure & anti-wear properties were investigated by means of coke test of internal combustion engine oil, oil-water separation test of marine and four-ball machine test. The results show that with the increase of base number of detergent, the high temperature detergency, water separation property and extreme pressure & anti-wear property of oil samples are improved. Among them, the high temperature detergency and water-oil separation performance of oil samples are greatly affected by the change of detergent from low base number to high base number, but are less affected by the change of detergent from high base number to ultra-high base number. With the increase of base number, the extreme pressure & antiwear property of the oil sample is enhanced. The friction protective film formed by the alkaline components of detergent has a certain extreme pressure & anti-wear properties under low load, while the extreme pressure & anti-wear properties of the friction protective film will weaken or even fail under high load.

Key words: base number, calcium sulfonate, high temperature detergency, oil/water separation, extreme pressure &, anti-wear