At the National Commodity and Derivatives Exchange, refined soya oil for delivery in October declined by Rs 3.55, or 0.63 per cent, to Rs 560.70 per 10 kg with an open interest of 1,14,740 lots.
Similarly, the oil for delivery in September weakened by Rs 3.05, or 0.50 per cent, to Rs 607.60 per 10 kg in 47,200 lots.
Analysts said offloading of positions by speculators, driven by low demand in the spot market against adequate stocks position, weighed on refined soya oil prices at futures trade.