Greek shipowner Tomasos Brothers has ordered four 37,500-dwt products tankers at Guangzhou Shipyard International (GSI) in China.
The owner revealed that it has converted an existing deal for the final two of four 52,000-dwt ships into the four smaller vessels.
The new quartet is costing $36m each, or $144m in total, as opposed to $100m en bloc for the two bigger ships.
The four vessels will be delivered at three-monthly intervals from the end of 2013.
The owner still has the first two of its 52,000-dwt series being built for hand-over in 2013, delayed earlier this year at the Greek company's request from 2012.