The nearest expiration date for Los Angeles CARB Diesel (OPIS) Futures (Oct 2016) is Oct 31, 2016.
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 Los Angeles CARB Diesel (OPIS) Futures (Oct 2016) before Oct 31, 2016.