The nearest expiration date for Gasoline Euro-bob Oxy NWE Barges (Argus) Futures (Sep 2013) is Sep 30, 2013.
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 Gasoline Euro-bob Oxy NWE Barges (Argus) Futures (Sep 2013) before Sep 30, 2013.