LONDON, Oct 11 (Reuters) - Differentials for Nigerian crude oil grades continued to crash on Friday with the key grade being shown at its lowest level since 2005 owing to still rising freight rates as a result of U.S. sanctions on China's shipping company COSCO. * Phillips 66 tentatively chartered a supertanker to ship U.S. crude from the U.S. Gulf Coast to South Korea for a record $14 million this week, sources said Thursday. * Traders and ship brokers said that rates were still rising beyond that level and that Bonny Light had been offered down to around dated Brent flat, down from close to a $2.50 premium to dated Brent last week. * In the Platts window, Cepsa bought a cargo of Amenam at dated Brent minus $1.55 cents a barrel from Total loading Nov. 10-11. * Bonny Light and Qua Iboe typically trade no more than $1-$1.10 a barrel above Amenam, further illustrating the market collapse, a trader said. * Forcados crashed earlier this week after Trafigura sold a cargo $1 below an offer level on Monday. * Cepsa also bought Bonny Light and Abo from Eni and Escravos from Equinor, traders said. Price details did not immediately emerge. TENDERS * India's IOC awarded its latest tender for west African crude loading Nov. 24 to Dec. 3 to Total, Chevron and Shell. * India's HPCL issued a buy tender for crude loading in the first quarter of next year. Details will emerge next week. RELATED NEWS * Highly sought after types of oil best suited to making cleaner shipping fuel are suddenly finding they are a tougher sell for thirsty East Asian markets, traders say, in an unintended consequence of U.S. sanctions on a Chinese shipping fleet. (Reporting By Julia Payne; Editing by Kirsten Donovan and Deepa Babington) ))