Express carrier Federal Express Corp. has changed its formula for imposing fuel surcharges on U.S. domestic and U.S. outbound shipments to one the carrier says is more closely related to the cost of jet fuel.

Under the new policy, the surcharge is subject to a monthly adjustment based on the average U.S. Gulf Coast spot price for a gallon of jet fuel as published by the U.S. Department of Energy. The immediate result of the change was a reduction in the fuel surcharge from 4 percent to 3 percent, beginning earlier this month. (The November fuel charge is based on the September average.)

Any fuel surcharge changes will take effect on the first Monday of each month. FedEx says information on any adjustments will be made available on its Web site, fedex.com, two weeks before the changes become applicable.