My '80 300D suddenly started having problems. I was on the freeway
heading up a hill at ~60 mph when RPMs started declining. It got to the
point where I could drive about 25 mph max. The car idles fine, and
accelerates great from 0-25, but after that it starts having power
loss, partciularly on any grade. On a significant grade the car will
slowly grind to a halt. If I stop for a minute or two on the hill it
will start out strong again but then quickly lose power.

Note that I had the oil changed right before this happened, so I'm
considering that they could have screwed something up, but I can't see
anything obvious that could have caused this.

My initial thought (and hope) is a clogged fuel filter. I'll trying to
find a replacement today. Any other thoughts?

Rip