Here is my catharsis on my old diesel........

In my old 300sd I used to change mine every second time I changed the
oil and filter (6K miles). We had dodgy diesel fuel in town because
not enough people used diesel at that time. If I bought my diesel on
the interstate at a truck stop where there was more usage and the
diesel did not sit in tanks for as long a period of time, the fuel
filters did not need changing as much. I would also blow out the air
filter with an air compressor and rotate it 180 degrees, and check the
banjo fitting, throttle linkages and little micro switches on top of
the valve cover as well. I only used Shell Rotella oil and Mann
filters.

Every third oil/filter change I would adjust my valves and replace the
air filter.

Every fifth oil/filter change I would change the transmission fluid
and rear axel fluid.

This schedule along with keeping an eye on motor mounts and replacing
them as necessary kept the old girl (Stella, my streetcar....) running
smoothly enough to stack wine glasses on the hood and she started
everytime.

Back on the old Mercedes mailing list, Stu Ritter had a tweak to
adjust the ALA compensator for the turbo charged models. It is a very
delicate adjustment that allows the altitude compensator to inject
more fuel (basically adjusted by Bar) and the turbo to kick in a bit
earlier (as I remember). The problem with the adjustment was that if
you turn the screw to far you broke a little ceramic bit in the ALA
and trashed it (expensive). I performed the adjustment on my car and
noticed a fairly remarkable increase in power  resulting in a slight
increase in exhaust soot and a slight decrease in mileage. Later I
backed it out. YVMV, and I do not recommend the change.

I also made sure all of the throttle linkages had the correct
measurements in mm (yes there is a spec on that and it is important),
replaced the Rack Damper spring with the stiffer one and made sure it
was in synchronization. adjusted the transmission modulator to the
point of a reasonably stiff but not head snapping shift (better
transmission life), and replaced the flex disks, motor and
transmission mounts. The cruse control amp needed resoldering, and the
tachometer amp/sender needed replacing once. I also replaced the
plastic bushings on the rear torsion bar that cause that annoying
thump when going over bumps.

That is about it other than tires, belts, brake shoes/rotors and brake
fluid, glow plugs, a battery, wiper blades and washer fluid.
Occasionally I needed to take the console switches out and clean them
too, when the fader control messed up the radio because I spilled
coffee. I also often needed to either replace or clean fuses,
especially in damp weather.

All in all that car ran pretty much flawlessly and lasted seventeen
years and almost 300,000 miles before I sold it (as far as I know it
is still going) for $4000.00. It did not use oil, the transmission
still shifted crisply, although it was getting a little slow going
into reverse.

No mcbrue, it never left me by the side of the highway and Hanz and
Franz never got their mitts on my car. I found a good honest Mercedes
diesel mechanic locally and he could always advise me or do stuff on
the car when I was too busy or it was beyond my competency. Yes the
rexus is probably less effort, but as you point out, not nearly as
much car.

me
- driving over the bridge with the trailer under it down by the river.