Oil is increasingly getting more expensive before it even reaches a refinery. Freight now accounts for roughly a fifth of the cost of a crude cargo, turning the tanker market into a major driver of the price buyers pay. At the center of the squeeze is the very large crude carrier, or VLCC, the supertanker that can move about 2 million barrels in a single voyage. Amidst stranded Gulf and Red Sea supplies, these vessels are spending more time at sea as refiners search farther afield for supplies.