Brent crude futures settled down $1.71, or 2%, to trade at $83.63 a barrel, having retraced some earlier gains.
West Texas Intermediate (WTI) crude futures were down $1.66, or 2.1%, at $76.28 a barrel.
Brent ended the week down 4.6%, while WTI fell 4.7%.
Brent and WTI's market structure implies current demand is softening, with backwardation, defined by front-month prices trading above contracts for later delivery, having weakened markedly in recent sessions ,.
This is starting to hit fuel demand, with traffic drifting down and implied oil demand around 1 million barrels per day lower than average, an ANZ note showed.
Oil prices steadied on Friday, but fell for the week on a stronger U.S.