The mildest winter in four years is prompting Japan to export its biggest volume of kerosene in a quarter century, squeezing profits for Asian refiners while cutting fuel expenses for airlines.

Japan has shipped enough of the transportation and heating fuel since December to fill a very large crude carrier, the most in at least 25 years, according to the Petroleum Association of Japan. January temperatures in Tokyo were the highest for the month since 2010, the Meteorological Agency said.

Asia's regrade, a measure of the profit from producing kerosene or jet fuel instead of diesel, will widen to a discount of $1.50 a barrel from April to June, compared with 60 cents so far this month, said IHS Inc., an industry consultant.