Net income for the three months ended Sept. 30 fell to $3.72 billion (EUR2.58 billion), or $1.75 per share, compared with $5.02 billion, or $2.29 per share, during the same period a year earlier.
Analysts polled by Thomson Financial had been expecting earnings of $2.07 per share, on average.
Chief Executive Dave O'Reilly said weak refining margins were the culprit behind the big drop.
"Margins were squeezed as escalating costs for crude-oil feedstocks could not be fully recovered in a U.S. marketplace that was well-supplied with gasoline and other refined products," he said in a statement.
Revenue also fell short of forecasts, increasing to $55.17 billion (EUR38.25 billion) from $54.21 billion a year ago. Analysts expected revenue of $58.29 billion (EUR40.41 billion), according to Thomson.
The discovery of the submarine has unveiled a few "inconsistencies." For example, how can one explain the fact that the sub was found where it needed to be searched for from the start?