Although not specifically about the Antara this piece shows the thinking of GM and their engines. There is a sentence in there about reducing "particulate" in the engines.
http://www.businesscar.co.uk/news/2013/vauxhall-cleans-up-with-engine-range-overhaul
enjoy
http://www.businesscar.co.uk/news/2013/vauxhall-cleans-up-with-engine-range-overhaul
enjoy