The Iran conflict has sent tanker rates soaring, forcing sellers to deepen discounts on heavy crude grades and giving US Gulf Coast refiners a cost advantage over Asian rivals, executives said after reporting bumper third-quarter profits.     Security threats around the Strait of Hormuz, a key maritime chokepoint through which about one-fifth of global oil and liquefied natural gas supplies passed before the war started, have disrupted tanker traffic, while higher war-risk insurance premiums and longer voyages have driven up shipping costs.     The disruption particularly benefited US Gulf Coast refiners, which could buy discounted heavy crude produced closer to home, including from Canada and Venezuela, while Asian rivals faced sharply higher freight and insurance costs to import similar grades through longer and riskier shipping routes.     US refining margins more than doubled in the third quarter.     Rising freight costs have widened discounts on Canadian heavy crude, including Western Canadian Select (WCS), which typically trades below US benchmark West Texas Intermediate (WTI), creating a windfall for Gulf Coast refiners, as more than 70 per cent of their facilities are configured to process heavier crude.      "The main story right now in the market is freight rates," Randy Hawkins, vice president of crude and feedstocks supply and trading at Valero Energy, said on a post-earnings conference call.     Freight costs for shipping crude from the US Gulf Coast to Asia have jumped to $30-$35 a barrel from about $5 a year earlier, Hawkins said.     "Higher freight rates actually give us an advantage into the typical export markets into Latin America," said Gary Simmons, chief operating officer of Valero, adding that it mainly competes with European barrels in that market.     Ample heavy crude supplies from Canada and Venezuela, combined with elevated freight rates, have widened the WTI-WCS differential, lowering feedstock costs, US refining executives said.     For Phillips 66, every $1 widening in the WCS-WTI differential is worth about $140 million in gains, Brian Mandell, executive vice president of marketing and commercial, said.     Higher shipping costs have also been more than offset by stronger fuel margins, said Delia He, an oil and tanker market analyst at Arrow Shipping.     "For every extra dollar of freight, the diesel margin has grown by at least eight," He said.     US refiners have also been shielded from the impacts of higher spot tanker rates following the war due to their advance shipping arrangements.     Phillips 66 said it had secured more than 40 time-charter vessels before the Iran conflict, covering about 40 per cent of its asset-based shipping needs.     Valero, PBF, Marathon and Canada's Suncor also secured chartered fleets before the war began, insulating them from the surge in prices.     Wider differentials are expected to continue to lend strength next year as well, some industry executives said.     Top US refiner Marathon Petroleum expects record Canadian heavy crude processing in the fourth quarter, while CEO Maryann Mannen has said that margins are expected to remain elevated through at least mid-2027.    

"In the near term we will take advantage of it," HF Sinclair said of the wider discounts, adding, "we do see the differentials stay wider than they have throughout the near term, at least through 2027."