It depends on temperature. At ambient temperature it is 1475 nJ/(kg K). Look at https://fr.wikipedia.org/wiki/Acide_oléique (the english page does not content info on Cp) for other temperatures.

https://www.chemeo.com/cid/13-615-4/Oleic-Acid also gives this information.

It is approximately 2.0 kJ/kg oC or 0.5 cal/g oC at room temperature

The specific heat capacity of oleic acid varies depending on temperature and phase, but a typical value for liquid oleic acid at around 25°C is approximately 2.02 J/g·K (or 2020 J/kg·K).