X-ray photoelectron spectroscopy was performed directly on neat zinc bis[O,O-bis(2-ethylhexyl)] dithiophosphate liquid. Data were collected on the liquid oil placed in a recessed gold-coated sample holder without any specific precautions relating to outgassing or charge compensation. The compound is of a class of zinc dialkyl dithiophosphates (ZDDP) employed as anti-wear additives in modern motor oils. Our lab is advancing the study of the interactions between ZDDP and other additives in fully formulated engine oils. ZDDP is manufactured by neutralization of dialkyldithiophosphates with zinc oxide. The O 1s core level was found to be composed of two peaks, a higher binding energy state attributed to the ZDDP complex, and a lower binding energy inorganic peak (about 10 percent contribution) attributed to the presence of unreacted zinc oxide. This lower-binding-energy zinc oxide peak did not increase after consecutive 10 min acquisitions. Thus, at the analysis parameters utilized in this work, XPS was achieved without noticeable decomposition of the ZDDP complex. This was supported by the fact that there was no apparent outgassing during acquisition. A constant vacuum pressure of 4.0 × 10−9 mbar was maintained during analysis of the oil. The C 1s core level envelope was fit by two peaks, aliphatic and ether, at a ratio of 6.42:1, respectively. The stoichiometry of 8:1 is expected for the RO-P group in this ZDDP, where R equals 2-ethylhexyl.