2. The premium is different. In the summer tourist season, the usage of crude oil is higher than that in winter. On the premise of constant supply, the contract price of crude oil in summer is higher than that in winter, resulting in a forward contract premium, while the demand for petroleum asphalt is relatively low and the price is lower than that of the forward contract due to the decrease of construction volume in rainy season.

3. Affected by fundamentals. When the fundamentals change, the near-month contract and the far-month contract will be affected differently. With the passage of time, the current main contract will gradually enter the delivery month, and the trading volume and positions will gradually decrease, while the trading volume and positions of the contract next month will gradually increase and become the new main contract. At this point, individual investors will need to switch to the new main contract in time for trading, which is also called extension.