(22 Nov 2020, 5:56 pm)Malarkey wrote Interesting they'd rather keep Euro 4 rated Omnicities over Euro 5 rated Mercedes Citaros with the exception of 5481-87 which are Euro 4, same again keeping Omnidekkas that are Euro 4 over the Presidents that are Euro 5, surely you'd be wanting to keep the fleet with the most efficient vehicles, Only Omnidekkas that are Euro 5 are 6162 to 6171/76.
Euro ratings aren't based on efficiency, just emissions alone. Some enhanced Euro modifications, like adblue, may actually adversely affect efficiency (MPG). There are also plenty of older vehicles that can meet Euro 6 standard, but aren't efficient enough to really bother.