US West Texas Intermediate crude oil futures for November fell 9 cents at $77.77 a barrel at 08:44, after netting gains of more than 2% to settle at a 7-week high on Wednesday. WTI is set to rise around 8% in September, the strongest monthly increase since February.
ICE Brent for November fell 8 cents to $80.69 a barrel after breaking above $80 for the first time since August.
"WTI went above the 200-day moving average and it may try to test above $78 today," said Ken Hasegawa, commodities sales manager at Newedge Japan.
Brent's break above $80 would "make some room for further gains to $82-$83," he said.
US crude stocks fell more than expected while oil product inventories slid against expectations of a rise in supplies, boosting market sentiment on Wednesday.
On Wednesday, trading volume in the United States spiked to more than 700 000 lots with activity picking up just before midday as WTI crude futures traded above their 200-day moving average of $77.51 per barrel.
A weaker dollar and possible gains in gold may also allow crude to rise further, Hasegawa said.
The dollar held near a five-month low against the euro on expectations of more Federal Reserve easing while gold stayed near Wednesday's record high.
The Reuters-Jefferies CRB index hit 8-month highs for a second straight session on Wednesday and was poised to end the third quarter up 10%.
However, US.crude prices are likely to remain capped below $80 as oil inventories are still high, Hasegawa said.
"There's no fear on supply shortage at the moment. I don't think market will go to $80-$90 levels."
