Refiners in the United States are processing more crude than at any time in eight years, and their biggest foreign supplier is about to send them less. Bloomberg reported on August 21, 2026 that Canada, which ships the US more than 4 million barrels a day, faces planned oil sands maintenance that Rystad Energy says will take about 300,000 barrels a day of production offline in September.
The timing is awkward. Government data cited by Bloomberg show refineries running hard to capture diesel margins that hit a record that same week. Alberta has little cushion to offer: its stockpiles sit at their lowest in more than a year.
The Midwest feels it first
Refiners in the US Midwest are the most exposed, since they rely on Canadian oil for about 70 percent of their supply. Energy Information Administration data showed US crude imports from Canada the week before fell by the most since May.
Canada has been a key supplier during the Iran War, which has curtailed Middle East exports through the Strait of Hormuz. On the Thursday of that week, a flare-up in tensions pushed US crude futures to their highest in several weeks. Bloomberg said the higher prices are likely to show up at gas pumps before the Labor Day holiday, when drivers usually take to the roads for the three-day weekend.
Premiums climb, pipelines loosen
Buyers are already paying up. According to Modern Commodities, the premium for diesel-rich synthetic crude over US futures rose to almost $20 a barrel the previous week, the highest since an April spike tied to the Iran War. That grade comes from oil sands bitumen processed in refinery-like upgraders.
Those upgraders are where some of the maintenance falls. Suncor Energy Inc. and Canadian Natural Resources Ltd. plan to shut equipment, including work at the Syncrude upgrader that was pushed back from earlier in the year.
Two of the main export pipeline systems offer another hint of lower volumes. Enbridge Inc. said on Wednesday it would not ration space on its Mainline, Canada’s largest oil export pipeline system, in September, citing maintenance at both production facilities and US refineries. The last time apportionment on the system was zero came in October of the previous year. The Trans Mountain pipeline from Alberta to the Vancouver area also stopped rationing space in August, for the first time in two months. Producers are no longer fighting for room, which suggests less oil is being shipped.
Storage tells a similar story. Kpler data put inventories at the Hardisty, Alberta hub near their lowest since March of 2025 and the second lowest level in figures going back to 2017. In March of that earlier year, companies had been rushing crude to the US ahead of tariffs that were expected to apply to oil.
