2T user here for 5months now, crdi engine runs quieter and smoother.

2T is more useful in Euro 4-6 diesels where sulfur is low. In our case, the real problem is dirty diesel. My guess is, by adding extra lubrication using 2T, it gives better protection or tolerance against abrassion on fuel-system parts.

Some readings:
http://www.dieselplace.com/forum/sho...d.php?t=177728