Nippon Oil Corp., the nation's largest refiner, will abandon a decades-old pricing method, breaking with common practice in an effort to boost transparency and pass on soaring crude-import costs, company officials said.

Nippon Oil plans Oct. 1 to start setting weekly wholesale prices for oil products, including gasoline and jet fuel, based on futures contracts on the Tokyo Commodity Exchange.

The company will abolish the practice of negotiated retroactive pricing, said two company officials with knowledge of the matter, who declined to be named before a statement due later this month.