(Recasts, updates prices, adds comment, changes byline, dateline; previous LONDON)
* Dollar falls to lowest vs yen since November 2014
* Oil renews price slide, weighing on risk appetite
* Chinese FX reserves decline, but less than feared
By Dion Rabouin
NEW YORK, Feb 8 (Reuters) - The dollar fell to a 15-month low against the yen on Monday as a renewed slide in oil prices and doubts about the effectiveness of the Bank of Japan's negative interest-rate policy drove investors back into the safe-haven currency.
After gaining overnight, crude oil futures again fell, weighing on investor confidence and sapping risk appetite. LCOc1 O/R
The surprising announcement that BoJ was cutting its interest rate to minus 0.1 percent on certain deposits sent the dollar up as much as 2 percent on Jan. 29. But markets have since reconsidered, with investors now buying the yen and selling the dollar.
Monday's price action chased the dollar to its lowest against the yen since mid-November 2014.
"A bit of it is positioning," said Charles St-Arnaud, senior strategist and economist at Nomura Securities International in London.
"They still believe that negative rates are the right policy for (the BoJ), but the market is starting to question the usefulness of the policy and how much of an impact it will have."
Because of its low interest rate, the yen is often used by traders to fund trades of more risky assets. In times of turmoil, investors unwind those bets and buy the Japanese currency.
The yen EURJPY= also gained more than 1 percent against the euro, touching a two-week high, as it benefited from its safe-haven status and worry over Europe's banks.
"The strong yen stands out," said Stephen Gallo, a BMO strategist in London. "As long as we remain in such a risk-off environment, there's no point in trying to catch that falling knife."
Against a basket of currencies, the dollar was flat at 97.062. .DXY over China's problems with growth, debt and the threat of currency depreciation may be on hold for the weeklong Lunar New Year holiday.
Data over the weekend showed the decline of China's foreign exchange reserves slowed to just below $100 billion last month. The drop was smaller than expected, but analysts said it was still a warning that Beijing must stem a flight of domestic capital or be forced to allow the yuan CNH= to weaken.
"My impression is that there is virtually no reserve armory big enough to cope with widespread capital outflows, if capital is allowed to flow relatively freely," Societe Generale (PA:SOGN) strategist Kit Juckes said in a morning note.
"Even if the market does calm down over the festive period, this is a story which will return."