US base oils supply rose to a four-year high in August, raising the prospect of a large build-up of surplus volumes.Domestic demand needed to extend its rise and exports needed to exceed 4 million barrels (563,000 tonnes) to halt any such rise in surplus volumes.Domestic demand duly rose in August for the third time in four months.US export data was exactly the same in August as the previous month both for the total volume and the volume of shipments to each country.The unusual data-pattern suggested that it could be updated in the coming months.For now, it complicated the calculation for the US’ total demand volume and subsequent size of any supply-build.Even so, total demand would need to be unusually high to match total supply of 7.24 million barrels (1.02 million tonnes) in August, government data showed..Supply rose to the highest since August 2021 amid a simultaneous jump in domestic base oils output and imports from overseas markets.Output of 5.53 million barrels in August edged up from 5.34 million barrels the previous month to the highest in forty-nine months.The July output volume was already the highest in more than three years..Base oils imports of more than 1.70 million barrels in August were the highest in nine months.The subsequent surge in supply put pressure on domestic and overseas demand to hold firm to absorb the volumes.It also left buyers and distributors well-prepared for any weather-related supply disruptions during the Atlantic hurricane season.An unexpectedly quiet hurricane season curbed the need to tap those stocks and raised the prospect of an even larger pick-up in surplus supply over the following months.A steady flow of Group II base oils shipments from US to India in September and October, and of Group I shipments to West Africa, pointed to such a dynamic.The shipments took place ahead and during the shutdown of a major Group II base oils unit in the US at the start of the fourth quarter.The shipments pointed to sufficient surplus availability even with the drop in output during the plant-shutdown..Brazil’s Sept base oils supply matches demand.Argentina Sept base oils supply exceeds demand.US’ July base oils demand rises