BP's pipeline carrying crude from the oil hub of Cushing, Oklahoma, to its refinery in Whiting, Indiana, began increasing rates on Friday, data monitor Genscape said on Sunday.
BP's massive 431,500 barrel-per-day refinery can run both sweet and sour crudes coming from pipelines in both Canada and the United States.
The ramp-up in rates on the U.S. line was on Friday, before the Saturday shutdown of part of Canada's Enbridge 14/16 main Canada-to-the United States pipeline after a fire in Illinois.
On Wednesday, rates on BP's U.S. line were cut back to 70,000 barrels per day, 105,000 bpd below normal levels, according to Genscape.
The line usually carries 175,000 barrels per day of West Texas Intermediate and West Texas Sour from the storage tanks in Cushing, northeast to BP's massive 431,500 bpd Whiting, Indiana, refinery, a major supplier of gasoline and diesel to the Chicago market.
A spokesman for Genscape said the refinery was running normally but the decision to cut back on the flow out of Cushing could be economic.
"BP could be maximizing the CDU that runs Canadian heavy crude while cutting back on the one that runs WTI and WTS," said Abudi Zein, a spokesman for Genscape.
"The other lines that we monitor and that could compensate are already running full," Zein said, adding that the outage will "blow out" the Canadian crude spreads.
Canadian crude is already heavily discounted to the United States WTI benchmark. On Wednesday, Canadian Heavy crude was bid at $35 under WTI while sellers were looking for $30 under. WTS is trading at about a $25 premium to Canadian crude, according to Reuters data.
Midwestern refineries have been running at record-high levels to take advantage of the price advantage of landlocked WTI and sharply discounted Canadian grades.