She said China is already influencing nearby markets. Traders in Singapore are closely watching the data related to China's refined oil exports.

And due to China's thriving diesel exports, diesel prices in Singapore fell from $130.22 a barrel in September 2012 to $117.19 a barrel in April this year, down 11.2 percent.

However, an anonymous insider who works at Sinopec said that supplying the domestic market is the company's primary task.

In addition to diesel, for the fourth quarter, Sinopec got 1.52 million tons of export quotas for kerosene oil, the fuel used in the engines of plants and for heating and lighting systems, up 74 percent compared with the last quarter.

"The increased export quota will be used in November and December, which means it may have a big impact on the Asia-Pacific market," said Li.

If Sinopec makes full use of its export quota in the fourth quarter, China's monthly average diesel exports will reach 500,000 tons by the end of the year, while during the first quarter, China's diesel exports averaged 280,000 tons per month.

In the second and third quarters, average diesel exports were 110,000 tons a month, affected by the quota limits at the time.

China's diesel exports have been increasing since last October when the country exported 144,000 tons of diesel, up 9.1 percent year-on-year. In November 2012, China's diesel exports reached 360,000 tons, a 490 percent increase year-on-year.

Last year, China added new annual refining capacity of 35 million tons, reaching 575 million tons nationally. The country's capacity is growing faster than demand, according to a report by the CNPC Economics & Technology Research Institute.

Refineries other than the top-three energy giants - PetroChina, Sinopec and CNOOC Group - are also growing with bigger refining capacity, accounting for about 20 percent of the country's total capacity.

However, due to the slowing demand for refined oil products, the growth rate of diesel output was only 2.4 percent in 2012.