The US has moved to end a ban on seaborne crude exports that has been in place for 40 years. The short-term significance is likely to be marginal given that the US remains a substantial net importer of crude and such imports have again edged higher in recent months, with domestic crude production down by 400,000 b/d from its April peak of 9.5mn b/d.

But US refiners, which are mostly configured to running sour heavy crude have struggled to cope with the boom in light sweet shale-derived...