I was driving my 2004 C320 Sport Sedan w/ 76K mi on the interstate a couple wks ago and a warning light came on to add 1 qt of oil, but disappeared after 5-10 min, only to recur 15 min later to add 1.5 qts x 5-10 min and then came on again to add 1 qt of oil. When I got home I lifted the hood in search of a dipstick, as I have never seen oil on the garage floor or smoke. Of course, there was no dipstick, so I went to the car's dash menu and was able to bring up varying amounts of oil to be added ranging from 1-2 qts. I went to dyno mode. and it read 6.2 qts in the engine. The warning light that first presented on the interstate has never repeated itself since then. I ord a generic MB shop dipstick, but when I inserted it in the tube, it only went in 1/2 to 3/4's of the way, but yet still read full.

Any ideas other than take it to the dealer?

 

Are you able to have any codes read off the DTC? This may give you a good place to start troubleshooting.