The latest increase added to the previous week's build of over 10 million barrels, which was the biggest in 14 years.
The dollar rose against a basket of currencies on Wednesday, recouping some of the previous day's sharp losses.
Asian stocks outside of Shanghai erased losses to end higher on Wednesday, but the mood was cautious ahead of the Federal Reserve's policy decision.
Stocks dropped sharply on Tuesday, as earnings disappointed as did durable-goods data.
US stock index futures signaled a slightly higher open, with European stocks boosted early in the day after Apple smashed analyst expectations.
European markets closed down on Tuesday, after a number of Wall Street's biggest firms missed earnings expectations.
Gold struggled on Tuesday to recover losses from the previous two sessions as a firm U.S. dollar and strength in equities dulled the metal's appeal.
Oil rose more than 3 percent on Tuesday as a weaker dollar propped up commodities priced in the currency.
The euro rose against the dollar before a meeting of the U.S. Federal Reserve that may push back expectations for an interest rate rise.
Asian shares hit fresh highs on Tuesday, as investors deemed a Greek exit from the euro zone unlikely.
U.S. stock index futures signaled a sharply lower open as major U.S. corporates missed fourth quarter earnings expectations.
Stocks were near unchanged on Monday, with Greek election results already discounted by investors.
U.S. government debt prices strengthened after investors flocked to safety following the victory of anti-austerity Syriza in the Greek election.
European markets closed higher, as investors digested news that Syriza had won the Greek general election.
U.S. oil prices were steady Monday, ahead of the first big snowstorm this year in the country's Northeast.
The euro regained a foothold in early deals in London, investors choosing to take some profit on two days of steep losses.
Gold fell 1 percent on Monday as traders cashed in gains that took the metal to five-month highs last week.
Asian equities reacted nervously to the election victory of Greek leftist party Syriza on Monday.
U.S. stock index futures turned to trade mostly higher early Monday, but uncertainty about the future of the euro zone hung over the market.
Stocks wobbled Friday, a day after the ECB unfurled a large asset-purchase program.
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India's economic growth slowed to 7 percent in the three months through June from 7.5 percent in the previous quarter, data showed on Monday.
Euro zone annual inflation came in at 0.2 percent in August on Monday, marking a stable reading for the second month in a row.