I have a lift and many of the special tools needed to service these cars. All work is done by me at my garage, the only time I use the dealer is if I have an issue that requires the SDS system. Over the last decade I've been to the dealer once and I'd call myself a fairly advanced DIY'er on the skill level scale. My time levels should fall on the lower end of the time scale.

For the last year I added up the time for repairs/maintenance on 3 of the cars I'm responsible for.

1) W124.128 - total time 12.5 hours
2) W210.025 - total time 9 hours
3) W202.024 - total time 10.6 hours

I didn't have too many issued over the last year, the biggest job (from a time perspective) I had to do was an A/C condenser replacement on the W210.025 and IIRC that job took around 4-5 hours to complete. These figures could really go up if major work was be required.

These times do not include washing/waxing but my cars only get waxed maybe once a year and I'd guess I might wash them 4-5 times per year so maybe add 12-15 hours total if you wanted to include cosmetics.

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98 Dodge-Cummins pickup (137K)
13 GLK250 (157k)
06 E320CDI (341K)
16 C300 (89K)
82 300GD Gelaendewagen (54K)