President Trump's decision to impose a 10% tariff on Canadian energy imports, effective February 4, is expected to widen the WTI-WCS price spread and increase costs for U.S. refiners and consumers, according to Citi Research. The tariff could push the WTI-WCS differential from approximately $15.5 to $18-20 per barrel, impacting U.S. domestic crude prices and potentially raising retail fuel prices by up to 10%, or 15-20 cents per gallon. "US Midwest and Rockies refiners could face pressures to their refinery margins," Citi analysts note, as they may need to source alternative crudes, driving up WTI prices relative to international grades. The tariffs are part of broader trade measures affecting Canada, Mexico, and China, with potential implications for global GDP and trade growth, which could exert bearish pressure on oil prices.