I went from a 4.8 to a 3.5d and really haven't noticed any real difference (except the much better gas mileage ).

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2012 F10 550xi Carbon black/oyster
2011 E92 M3 SSII/black
2012 W166 ML63 Steel grey/porcelain
2007 E93 monaco blue/beige (retired)
2010 E70 35d Space grey/saddle brown (retired)