Nissan sales more than double year-on-year in Singapore. The Singaporean new car market is off -5.9% year-on-year in March to 2,469 sales, bringing the year-to-date tally down -17.4% to 6,493. Once again Toyota (-16.4%) falls faster than the market but scores a solid 21.3% share vs. 20.3% year-to-date. Mercedes (-5.4%) roughly…