Chinese can always buy oil through their dummy companies in South Eastern Asian countries.
Even if Indian successfully identify and lock up every third party oil tank smuggling for China, it is still hardly to bleed Chinese industries:
Currently, Chinese domestic oil production counts 32% of total oil consumption, however, they have the capacity to expand to 50% in short notice. At the meantime, they can increase their purchase from Russia, South America, Canard, and ......USA. These may not make up 100% of loss caused by India block, but already more than enough to keep the Industries and war machine running. The group that will be impacted by India block is the private car owner.