Try a whole bottle in a tank, not just the two ounces or so. It raises the cetane index more, and increases the ignitibility of the fuel. This will reduce or eliminate knock if it is due to poor fuel spray or a carboned up injector.

To have the old style injector seals you would have to have something as old as 1972 or so, and they would have to be either original or so badly stuck they couldn't be removed -- that is why I still have one in the 220D -- I can't get it out. they go into the hole at the top of the prechamber, not just on top of it like the new ones. If you get the new ones upsidedown, they leak, and you have low compression.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!