Barclays pointed out in a report on China energy demand back in October that improving industrial activities and new refining capacity in China are fueling the pick up in demand.

FORBES: China Wants More Oil

Now, China appears to be picking up this newly available market share, a mutually beneficial arrangement, as Iran needs the gasoline and China has surplus refining and shipping capacity.

FORBES: China Boosts Gas Sales to Iran, Irks U.S.

But, even if China had heavy-crude refining capacity--which it doesn't--it wouldn't make economic sense to trade the four-day boat trip to Houston for a 40-day ride across the Pacific.

FORBES: Hugo's Folly

In China, where much of the growth in oil demand is generated, 80% of refining capacity is dedicated to sweet crude.

FORBES