A record number of supertankers is steaming toward the U.S. to load oil as shipowners look to capitalize on an increase in the nation’s crude exports. 

Forty-eight vessels are bound for the country in the coming three months, according to data gathered November 3 by Bloomberg. That’s the most in at least six years. 

The flow of vessels illustrates the changing energy landscape as the U.S. pumps more crude than ever before and the Organization of Petroleum Exporting Countries and its allies seek to prop up the market with supply curbs. U.S. crude exports have surged this year, government data show.

U.S. producers are increasingly sending low-sulfur “light-sweet” oil overseas, while many domestic refiners prefer to fill their slates with heavier grades that yield more diesel-type fuels. The nation lifted its decades-old restrictions on crude exports in 2015.

“U.S. slate-optimization is forcing further volumes of U.S. light sweets to the waterborne market,” said Richard Price, an oil markets analyst at Energy Aspects Ltd. 

Shipments from the U.S. Gulf Coast — the main exporting region — are expected to rise by 100,000 barrels a day year-on-year in December, to 4.1 million barrels a day, according to the researcher. Meanwhile, the OPEC+ curbs are prompting tankers to leave the Middle East in search of better prospects in the Atlantic for the winter season, he added.

The glut of vessels racing to the U.S. Gulf even includes ships heading to the region on a speculative basis without any cargo booking, an industry practice known as ballasting, according to EA Gibson, a London-based shipbroker. 

Stronger demand for winter could mean higher earnings for those tankers when they reach the U.S., according to Svetlana Lobaciova, a principal analyst at the firm.