Mainland Chinese shares posted substantial gains after recent sharp sell-offs. The Shanghai Composite Index climbed 1.6 percent to 2,061.79. The smaller Shenzhen Composite Index jumped 2.1 percent to 786.05.Benchmark oil for January delivery was up 1 cent to $86.27 in electronic trading on the New York Mercantile Exchange. The euro fell 0.2 percent to $1.2938. ___ Pamela Sampson in Bangkok and Fu Ting in Shanghai contributed to this report.