Presence of oleanane in crude oil is now considered as the age indicator of source deposition assuming the biomarker has been migrated with oil from the source rock. Possibility of contamination of the same biomarker in reservoir has so far been ignored. In this work, attempt has been made to see the possibility of reservoir contamination of 18α(H)-Oleanane in crude oil. A mixture of standard oleanane with saline water is first used to saturate a core, and then gasoline (free of oleanane) is used to displace the water in the core. Extracted gasoline from the core is then analyzed to check the presence of oleanane. Results show appreciable concentration in the extracted gasoline suggesting gasoline can be contaminated with oleanane if reservoir is deposited in oleanane-rich water.