FWIW...
I kept a spreadsheet to document the costs of running my dear departed 1984 300D.
This was a car that started out as a nice clean rust-free example with a few minor flaws. I lovingly maintained that car, rebuilt the front end, brakes, and changed out various bits & pieces over the years. In addition to the usual w123 stuff, like motor mounts, injector nozzles, and fluids, filters, belts, vacuum pods, I pulled the head to do a valve job and installed a new water pump, thermostat, and radiator. I also tweaked a few things here and there (boost controller, trans vacuum system, etc., etc.) so that it drove like a proper w123 should.
I did (almost) all of the work myself, using
good quality parts.
When I sold it (which I shouldn't have done!) I received almost one thousand dollars more than I originally paid for it. So, the bottom line:
Over approximately 14 years of ownership, my actual monthly cost of ownership, minus registration, insurance, and fuel was....
$28 per month.
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Current rolling stock:
2001 E55 183,000+ Newest member of the fleet.
2002 E320 83,000 - The "cream-puff"!
1992 500E 217,000+
1995 E300D 412,000+
1998 E300D 155,000+
2001 E320 227,000+
2001 E320 Wagon, 177,000+
Prior MBZ’s:
1952 220 Cab A
1966 300SE
1971 280SE
1973 350SLC (euro)
1980 450SLC
1980 450SLC (#2)
1978 450SLC 5.0
1984 300D ~243,000 & fondly remembered
1993 500E - sorely missed.
1975 VW Scirocco w/ slightly de-tuned Super-Vee engine - Sold after 30+ years.