Futures fell 2.5 percent in New York. China’s oil refining dropped the most in three years in July, while crude output retreated from the highest this year. Libya’s biggest oil field, Sharara, cut output by more than 30 percent because of security threats, a person familiar with the matter said. Meanwhile, the dollar strengthened, eroding the lure of commodities as a store of value. "We’re seeing some strength in the dollar, and the preponderance of news seems to be favoring the bears right now," Phil Flynn, senior market analyst at Price Futures Group Inc. in Chicago, said by telephone. "If you look at the China data this morning, when it came to the China refinery runs being down in July, that’s adding to the perception of slowing demand, and it’s offsetting the concerns about Libyan oil production." Click Read More below for additional detail.

“The rise in oil prices has mainly been caused by the freezing polar vortex hitting the U.S., firing up heating demand, and spurring concern about a potential impact on oil production and trade,” said Jens Naervig Pedersen, an analyst at Danske Bank A/S in Copenhagen. Oil has risen for two years running as the Organization of Petroleum Exporting Countries and Russia led a coalition of oil producers in cutting output. Prices have also been boosted by stoppages at pipelines in the U.K. and Libya. However, they are now at levels that are expected to help U.S. shale producers ramp up drilling, unlocking more crude and undermining OPEC’s efforts. Click Read More below for additional information.

Ahead of next week's OPEC meeting in Vienna, strategists are closely watching swings in crude oil prices, which are faltering after weeks of gains. Despite political tensions involving oil superpower Saudi Arabia and OPEC's promises to cut production, crudeprices could come down by year-end, one strategist says. Here's why. • "Tensions in Saudi Arabia are still flaring following the actions by Crown Prince Mohammed bin Salman," Chantico Global CEO Gina Sanchez said Monday on CNBC's "Trading Nation," referring to a vast political shakeup in the kingdom earlier this month that initially boosted oil prices. • It is unlikely, however, that this will be an "actual geopolitical event," Sanchez said, and oil prices should continue settling. Click Read More below for additional information.