Markets were mostly higher on Thursday.
The S&P 500 rose 0.2 percent and the STOXX Europe 600 rose 0.7 percent as US crude rose 3.1 percent.
Earlier on Thursday, however, the Nikkei 225 tumbled 1.6 percent.
While US stocks rose on Thursday, a CNBC report suggests that the rally in stocks may have peaked.
It said that the advance-decline line of stocks on the New York Stock Exchange, which had risen to its highest in more than 12 months recently, has turned a touch lower, indicating a loss of momentum.
Breadth has also declined, with 76 percent of the sub-industries in the S&P Composite 1500 trading above their 50-day moving averages on Tuesday, down from 95 percent on 15 July.
All this is occurring as investors have become more optimistic. The AAII Investor Sentiment Survey and US Investors Intelligence survey showed bullishness among investors rose in the last week to 35.6 percent and 56.2 percent respectively.
The Investors Intelligence newsletter's co-editor John Gray said the above-55 percent level of bullishness "is considered the danger level" for the stock market.