Warren Buffett has been vocal about his support for Detroit as it tries to recover from its bankruptcy. He's also putting some money behind those words.» Read More
Spare a thought for Warren Buffett, whose portfolio is not doing him any favors this week.
On Monday, Buffett lost nearly $1 billion on his third-largest investment, IBM, after the company posted disappointing earnings.
Read MoreBuffett sells 'huge mistake'
Coke is Buffett's second-largest investment and has been one of the stalwarts of his portfolio for decades. (He left Coke's board in 2006 and his son Howard took a board seat there in 2010.)
With 400 million shares, Tuesday's decline of $2.72 cost the Oracle of Omaha $1.09 billion. Shares were on track for their worst day since October 2008. (With IBM's $7 decline on Tuesday, he was out another $494 million there, too).
"I love Coke. I love the management, I love the directors," Buffett said in a CNBC interview in April, while discussing the recent controversy over the company's executive pay plan.
He has described buying into the stock as a "huge mistake."
Warren Buffett does not like to lose money in general, so losing $1 billion before lunch on a Monday morning can not be going down well.
The plunge in IBM shares Monday after its weak earnings results cost the Oracle of Omaha dearly. The stock fell $13.06, and Buffett held about 70.2 million shares as of June 30, according to the most recent SEC filings.
That means the sharp decline cost him $916.5 million—a drop in the Berkshire Hathaway bucket, to be sure, but still noteworthy. (At IBM's lows of the day, he was down as much as $1.08 billion).
Read MoreIBM on earnings: We're disappointed
In April, after a prior weak earnings report, Buffett told CNBC he had not "soured" on IBM, that he had bought more stock this year and that he had not sold a share.
IBM CEO Ginni Rometty dismissed talk of the tech company splitting up, despite its large size, Monday's earnings miss and the recent fad for tech companies to split in two.
Read MoreRometty: Clear path forward
"There is no doubt that marketplace speed has increased," she said in a CNBC interview. "We have a very clear strategy about how to take this company to the future."
Warren Buffett often makes investments that are out of reach for ordinary investors. But in the case of his recent car dealership deal, there's a rare chance to join him for the ride.
Last week, the Oracle of Omaha bought privately owned car dealership Van Tuyl Group for an undisclosed sum. The deal surprised some observers because annual domestic car sales have reached levels above 16 million—near a historical high.
The concern is that sales growth will be difficult to achieve and auto industry profits will stagnate. Indeed, shares of General Motors have fallen 24 percent so far this year while Ford has declined by 10 percent.
But Buffett recognizes that dealerships can thrive even without much growth in car sales. First, dealers can make just as much money selling extras like insurance and doing repair work. And given that the industry is very fragmented, it's reasonable to expect big players to scoop up smaller rivals through lucrative acquisitions over the next several years.
"With Tesco, we definitely made a mistake. I made a mistake on that one more than anybody else made a mistake ... That was a huge mistake by me," the billionaire told "Squawk Box" on Thursday.
The U.K. supermarket retailer has seen its shares fall more than 48 percent year to date. Buffett's investment firm Berkshire Hathaway is now nursing losses of more than $700 million. According to Berkshire's annual letter to shareholders, Buffett has 301,046,076 Tesco shares.
The man known as America's greatest investor isn't bothered by stock market volatility.
"I have no idea what the stock market's going to do tomorrow or next week or next month or next year," said Berkshire Hathaway Chairman and CEO Warren Buffett.
"If you own your stocks as an investment—just like you'd own an apartment, house or a farm—look at them as a business," Buffett advised. "If you're going to try to buy and sell them based on news or something your neighbor tells you, you're not going to do well. Find a good bunch of businesses and hold them."
"You will not make money trying to sell stocks daily or weekly," Buffett said.
For Larry Van Tuyl, it only took seven years to convince one of the world's best-known investors—and himself—that it was time to sell the family business.
Billionaire investor Warren Buffett told CNBC on Thursday he bought stocks in Wednesday's big selloff.
He won't name names or whether he was adding to positions of his current holdings. But he did describe them in a "Squawk Box" interview as "names you'd recognize."
Buffett said he likes to buy stocks when they go down, not when they go up. "The more [the market] goes down, the more I Iike to buy." He added that trying to time the market by buying and selling individual names often is a "fool's game."
Any investor who's owned a cross section of American business has done really well over the past 10 or 20 years, he said. Over time, values do appreciate—not for every stock, he said, adding the Dow Industrial Average was under 100 during his lifetime.
With all the talk on Wall Street about when and by how much the Federal Reserve might start increasing interest rates, Buffett said the central bank's moves have no bearing on his investment strategies. "I really don't care about whether the Fed is going to raise interest rates."
He said he buys businesses that he thinks will be good for the next 50 years—such as the deal he announced on CNBC Thursday that he's buying the nation's largest privately held car dealership group, Van Tuyl Group.
Warren Buffett is getting into the auto business.
The billionaire investor announced on CNBC on Thursday that he's buying Van Tuyl Group, the nation's largest privately held car dealership chain.
He expects to use this agreement as a vehicle to buy other dealerships. "We will hear, I predict, from hundreds of dealerships in the next year."