US oil refiners that have been among this year’s strongest S&P 500 performers are headed for a reckoning with a darkening supply-and-demand outlook. Marathon Petroleum Corp., Phillips 66 and Valero Energy Corp. are set to report their weakest quarterly profits in two years starting this week. For Marathon, the pain is expected to linger as the biggest independent US refiner by market value braces for a second consecutive year of declining sales — the first time that will have happened in almost a decade. Refining stocks started the year with a bang as a convergence of fuel-supply threats from the Red Sea to ... (full story)