I wouldn't put it in a 99, but the book for one of my W123s (and maybe all of the books) suggest that I fill a replacement fuel filter with ATF before I install it. I use diesel purge, but given the variety of material in biodiesel (virgin, wvo, vvo, etc) I can't imagine modern ATF diluted by that much diesel making any difference at all. As stated, used lubricants are a different story with their suspended metal bits.

-Tad

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1995 G320
2003 C230 Kompressor Coupe
2005 ML500
2007 ML350