Nymex December West Texas Intermediate lost 58 cents at $79.82 a barrel, while ICE December Brent slipped 64 cents to $78.25 a barrel.
US crude stocks fell 4m barrels last week, confounding the consensus market forecast for an increase of 1.4m barrels.
Although the drop in crude stocks was viewed as positive, the impact was offset by weak demand from refiners. Refinery utilisation fell 1.3 percentage points to 80.6 per cent of capacity.
Some traders expressed disappointment that the fall in refinery activity did not translate into more substantial decreases in petrol and heating oil stocks.
Petrol inventories fell 300,000 barrels, contrary to the consensus forecast for a rise of 300,000 barrels.
Distillate inventories (including heating oil) fell 400,000 barrels, below the consensus forecast for a drop of 1m barrels.
On Thursday, Nymex December RBOB unleaded gasoline traded 1½ cents, or 0.7 per cent, lower at $1.9972 a gallon, while Nymex December heating oil also lost 1½ cents, or 0.7 per cent, at $2.0740 a gallon.