 However, due to the large size of the vessels the emissions per cargo ton-mile are very low and thus the "Valemax" vessels are in fact among the most efficient long-distance dry bulk carriers in service — Vale has reported a 35% drop in emissions per ton of cargo carried in comparison to older ships.In the second series, the main engine has been changed to more efficient MAN B&W 7G80ME-C9 engine producing about at 72 rpm, and a further 15% to 20% reduction in carbon dioxide emissions is claimed.The Japanese-built ships have 7RT-flex82T engines rated at and 74 rpm, slightly less than their South Korean- or Chinese-built equivalents.