There should still be a dipstick tube on the car. As has been extensively debated here, Mercedes are designed so that the dipstick tube reaches the absolute bottom of the oil pan and is usually the preferred way to change the oil. I change the oil on my car with a MityVac suction pump.

I have not actually looked at the bottom of the engine on the C55, but I believe you will find a drain plug on the bottom of it. Remove the lower cladding and have a look.

Also, if you do a search on "topsider" or similar phrases you will encounter days worth of reading.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record