Brent and WTI closed the session at $93.99 and $88.06 respectively, leaving the transatlantic spread at $5.93. Over the past two weeks that spread swung between roughly $6 and $13; today it sits at the low end, which narrows the premium of light sweet crude over heavy sour grades and tilts the refinery feedstock choice back toward the heavy end.

For the transfer book the spread is not decoration. The seven STS grades — ESPO, Dubai, Oman, Urals, Basrah Light, Bonny Light and Lula — all complete title transfer through ship-to-ship transshipment, and freight, insurance and differentials are live variables in the delivered cost. Each one-point move in the spread shifts the buyer's lock-in point by half a step forward or back.

Crude rose across the board today: Brent +2.73 and WTI +2.35, yet the narrowing spread shows WTI tracking higher more tightly. Buyers priced off WTI got a cheaper lock than yesterday; those anchored to Brent saw the delivered cost partly offset by the tighter spread.

Operationally, when the spread dips below $6 the delivered economics of heavy sour grades — Basrah Light, Urals — improve relative to light grades. The transfer ledger should be repriced against the new spread for every cargo in transit rather than carried on last week's differential sheet.