The September/October cash roll, which allows traders to roll long positions forward, traded at minus 55 cents a barrel, dealers said.
Meanwhile, stocks at Cushing, Oklahoma fell by roughly 187,000 barrels the week to Aug. 19, traders said, citing data from energy monitoring service Genscape.
Light Louisiana Sweet for September delivery fell 3 cents to a midpoint of $1.52 and traded between $1.50 and $1.55 a barrel premium to US crude futures.
Mars Sour fell 10 cents to a midpoint of minus $2.85, trading between $2.70 and $3 a barrel discount to US crude futures.
WTI Midland rose 2.5 cents to a midpoint of minus 10 cents, and traded between a 5-cent and 15-cent a barrel discount to US crude futures.
West Texas Sour fell 35 cents to a midpoint of minus $1.60. It traded at a $1.60 a barrel discount to US crude futures.
ICE Brent October futures fell $1.76 to settle at $49.16 a barrel.
WTI September crude futures dropped $1.47 to settle at $47.05 a barrel.
The Brent/WTI spread narrowed 2 cents to settle at minus $1.75.