NEW YORK - Oil prices slipped on Friday, the last trading day of 2011, but still locked a gain of more than 8 percent for the year.

Light, sweet crude for February delivery slipped 82 cents, or 0.82 percent to settle at 98.83 dollars a barrel on the New York Mercantile Exchange. ?

After starting the year at the prices of 91.38 dollars a barrel, Oil went through severe ups and downs in the past year, with the prices approaching 114 dollars a barrel in April and plunging to about 75 dollars a barrel in October.

Although the weakness in the world economy cast a shadow on the demand outlook, oil prices continued to climb. Overall in 2011, crude prices averaged 95.09 dollars per barrel in New York, up from 79.64 dollars in 2010 and from 62.11 dollars in 2009.

At the end of the year, oil prices once again flirted with the 100-dollar-mark on geographic fears, especially after Iran threatened to close the Strait of Hormuz, a key shipping route for oil tankers

In London, Brent crude for February delivery also dipped and last traded around 107.5 dollars a barrel, gaining about 13.5 percent for the year.