I have used Red Line d.f. Catalyst since I first started driving Benz diesels. I had a friend that put over 300K miles on his W115 300D and convinced me it was beneficial, and it seemed to reduce nailing in my first non-turbo diesel. I used to buy it by the gallon jug then refill into the small 10 oz bottles, but after spilling some of it on the garage floor (it kinda stinks) I stopped that mess and now buy it by the case: http://www.importpartsspec.com/shop/mall/redline.asp
Dieseldiehard
'71 220 (gas) - latest project
'79 300TD w/ '85 turbo engine @ 279K
'83 300D @ 267K
'85 300TD @ 260K
all daily drivers