Not buying that it is loaded with oil. Iran is well known to smuggle weapons by sea.
https://www.navytimes.com/news/your-navy/2019/12/04/officials-warship-seizes-iranian-missile-components/
https://www.militarytimes.com/flashpoints/2020/02/19/ship-seizures-included-relatively-new-iranian-surface-to-air-missile-bound-for-houthi-rebels-in-yemen/