Diesel particulate filters (DPF) require routine cleaning to remove ash that builds up over time. Most vehicles using a DPF system will have an on-board filter service monitor to indicate the filter condition and guide your filter cleaning schedule.
In ancient times the islands formed an independent kingdom. Chinese and Japanese sovereignty were successively forced on the archipelago from the 14th to the 19th century, and in 1879 the Ryukyus became an integral part of Japan. After the defeat of Japan (1945) in World War II, the United States took control of the islands.
The Ryukyus extend southwest from Kyushu (the southwesternmost of Japan's four main islands) to Taiwan. The Okinawa Prefecture encompasses the southern two thirds of that chain. Naha, Okinawa's capital, is located in the southern part of Okinawa Island. Although Okinawa comprises just 0.6% of Japan's total land mass, about 75% of all U.S. military installations stationed in Japan are assigned in Okinawa. Currently about 26,000 of the U.S. troops deployed in Japan are based in the prefecture.