The nearest expiration date for Gasoil 0.1% Barges FOB ARA (Platts) Futures (Jul 2018) is Aug 7, 2018.
The best time to sell a futures contract is when you've already made money on the investment, but still have plenty of time left before the expiration date. Thus, a good option would be to sell Gasoil 0.1% Barges FOB ARA (Platts) Futures (Jul 2018) before Aug 7, 2018.