05 and 06 are the better years due to the om648 straight 6. The 07 went to the V6 which was (prior to release) rumored to be more powerful and have better economy. Those rumors were false, and later years had DPF and Adblue which are power and economy killers. Until the current 4 cylinder diesel of 2014 the OM648 is still considered to be the best choice in most owners views. The SBC repair can be pricey, but what MB repair is not? The benzworld w211 forum is actually a worthwhile place (wow did I just say that?!?)