China can control North Korea by treating to block the pipe line for petroleum

China can control North Korea by treating to block the pipe line for petroleum from China to North Korea, but China would not block the pipe line.

The oil produced in China to send to North Korea needs heat because the oil from China is getting hard without heat.
There is a line to heat the oil inside the pipe upto 70 celcius degree to keep the oil liquid.

From 1976 until 1997 North Korea imported about 1 million to 2 million tons of Oil but since 1997 the amount of oil imported to North Korea decreased to 4 hundred thousand to 5 hundred thousand tons.

Why?

Firstly, North Korea does not need any more oil for industrial use.
Secondly, in 1994 USA provided oil to North Korea on condtion that North Korea did not develop neclear weapons any more, but North Korea broke the promise and no more oil has been provided since then.
Lastly, the price of oil increased.

Recently the price of oil has been decreased. 
I wonder if North Korea would imports more oil from Chna because of low oil price?

http://www.yonhapmidas.com/article/160304163119_139835