South Korea’s four oil refiners posted combined first-half operating profit of 11.08 trillion won ($8 billion), reversing a 1.3 trillion won loss a year earlier. GS Caltex led with 4.19 trillion won, followed by HD Hyundai Oilbank with 2.76 trillion won, S-Oil with 2.20 trillion won and SK Energy with 1.93 trillion won. Much of the rebound came from temporary inventory gains after oil prices surged during armed conflict in the Middle East, leaving refiners exposed to negative lagging if crude prices fall before refined products are sold. Inventory-related gains across the four companies were estimated at 3 trillion to 4 trillion won in the first half, while each company could face about 200 billion won in inventory losses for every $10-a-barrel decline. The refiners are using the liquidity from the windfall to expand sustainable aviation fuel, biofuels, AI data-center immersion cooling and electric-vehicle lubricants.