| abstract |
An additive for oils is provided which comprises a zinc phosphate compound having a structure represented by formula (I) (wherein X1 and X2 are the same or different and each represents sulfur or oxygen, and R1 and R2 are the same or different and each represents an optionally substituted alkyl, etc., provided that the two R1's, two R2's, two X1's, and two X2's each may be the same or different) and either a guanidine compound represented by formula (II) (wherein R3, R4, R5, R6, and R7 are the same or different and each represents hydrogen, an optionally substituted alkyl, etc., provided that not all of R3, R4, R5, R6, and R7 are hydrogen) or a salt thereof. |