US base oils exports fell in August to an 11-month low amid signs of ongoing plant maintenance work and slowing demand in overseas markets.

Base oils exports of 1.23mn bl (173,240t) in August fell from 2.10mn bl the previous month, government data showed.

The July volume had been the second highest in more than four years. The August volume was the second lowest in more than two years.

The drop in shipments cut total base oils exports to 14.62mn bl in the first eight months of the year. The volume was less than 1pc higher than year-earlier levels of 14.52mn bl.

Exports in the first seven months of the year had been 7pc higher than year-earlier levels.

The volatility of export volumes in recent months mirrored a similar trend for domestic base oils and lube consumption in the US.

Domestic demand had surged then plunged several times since March partly in response to buyers' moves to lock in supplies ahead of further base oils and lube price increases.

The size of the change in demand contrasted with relatively steadier base oils output during that period.

The larger-than-usual divergence between output and domestic demand complicated producers’ inventory management and boosted the attraction of additional exports to clear any surplus.

The fall in base oils exports in August also coincided with sliding prices everywhere from Asia-Pacific to Mideast Gulf and Europe.

US producers’ posted prices held steady that month.  

The lower prices in other regions complicated the arbitrage to move US shipments to those markets.

The lower prices also facilitated arbitrage shipments from those markets to outlets like Latin America. The region is also a major market for US supplies.

The drop in US exports in August also reflected still unusually low shipments from districts like San Francisco.

A sharp slowdown in exports like that often takes place during plant maintenance work.