Sorry for being a luddite..
Just got my first Merc.. A 2010 C180 CGI Sport BlueEfficiency. Had a choice of 17 inch v 18 inch AMG alloys... Needless to say, went for the 18'. However a bit surprised that the 18' has a higher Co2 than 17'. Luckily it is the same VED band, but begs the...