Buffett Bets on Oil

Another reason for the investment, says Tilson, could be an attempt to hedge against Berkshire's other holdings that are heavily dependent on consumer spending, like Coca-Cola (KO Quote) and Nike (NKE Quote). If those positions were hurt as consumers struggle under the weight of rising fuel prices, investments in the energy market could offset those losses.

Berkshire recently announced plans to buy 80% of Israel's Iscar Metalworking. At its May 6 annual meeting, Buffett said he would like to cut Berkshire's cash stake, which recently totaled $42.86 billion, to about $10 billion.

"Conoco makes up a very small percentage of Berkshire's overall portfolio, so people probably shouldn't read too much into it," says Tongue.