S&P, a unit of McGraw Hill Financial Inc, cut Exxon's rating to "AA+" from "AAA," a one-notch demotion that leaves drugmaker Johnson & Johnson and Microsoft Corp as the only U.S. companies with the coveted, sterling rating that dozens of U.S. corporations enjoyed in the 1980s.
Though the downgrade was a symbolic blow for a company that prides itself on strength and discipline, the new S&P rating for Exxon is still as high as its ratings for the U.S. government bonds, widely seen as among the world's safest investments.
Shares of Exxon, which is slated to post quarterly results on Friday, shrugged off the news, rising 0.34 percent to close at $87.63.
Exxon and other energy companies have been under pressure to return money to shareholders. It spent $210 billion on share repurchases over the last decade, and during the fourth quarter, paid out $3.6 billion in dividends and share repurchases, more than it earned.
But in February, with oil prices having fallen in half since mid-2014, Exxon changed course and said it would only repurchase shares to offset dilution, as opposed to return cash to shareholders.
Still, S&P said Exxon's debt level had more than doubled in recent years due to growth projects including liquefied natural gas export facilities in Papua New Guinea, as well as dividends and other items, with overall spending exceeding cash flow.
In a statement about the downgrade, the world's largest publicly traded oil company made no indication it would make further changes in response to S&P move.
"Nothing has changed in terms of the company’s financial philosophy or prudent management of its balance sheet," ExxonMobil spokesman Scott Silvestri said.
Exxon added it values its strong credit position and will keep focusing on long-term shareholder value despite oil market volatility.
Moody's in February affirmed its "Aaa" rating for Exxon with a negative outlook. At the time, it encouraged the company to invest more in replacing declining reserves.
Last quarter, Exxon executives said they felt it was "important" to be ranked at the top of the ratings scale, as the rating was a sign of their superior business management amid the more-than 60 percent drop in oil prices since 2014.
"We get value from the 'AAA' credit rating," Jeff Woodbury, Exxon's vice president of investor relations, said on a February conference call in reference to cheap funding costs guaranteed by high ratings.
The downgrade was not a complete surprise. In February, S&P downgraded rival Chevron Corp and warned that such a move was possible for Exxon also.
"We believe the company may return cash to shareholders rather than building cash or reducing debt, limiting improvement in our projected credit measures when commodity prices improve," S&P analysts in a press release on Tuesday.
The downgrade comes as Exxon fights accusations it misled investors and the public about the risks of climate change.
(Reporting by Ernest Scheyder in Houston and Amrutha Gayathri in Bengaluru; Editing by Anil D'Silva; Editing by Terry Wade, Bernard Orr and David Gregorio)
By Ernest Scheyder