I did an oil change today. Oil level sensor said there were 7.8Qts (after the car had been sitting for about 30 minutes).

I pulled right at 10qts of oil out of the engine, as measured with my vacuum pump graduation marks.

The sensor still said there were 2.7 qts in the engine after pulling 10 qts out of it.

I added 10 qts of fresh oil, and what do you know? The sensor thinks there are 8 qts of oil in the engine. Is the oil level sensor really THAT inaccurate?

I can understand it being off by say, a quart, but almost three?

Glad to see someone else experiencing this issue. I believe there are two calulations or sensors. I think what is happening is somehow the sensor is based upon flow due to the fact when you rev, the quanity reduces and increases when the revs are at idle. But then again, when engine is off, it displays the message if oil is needed in quarts. That measurement is the important one.
Just my $.02

According to WebETM there are two oil level sensors indeed, based on the engine model.

On the 275 Engine it's sitting on the engine, and the 137 in the oil pan.

However, it would seem that there is only one oil level sensor per engine model though... :/

~shrug~

I'm going to pick up a proper oil dipstick for that engine. Apparently, it is available from MB, but most parts counter people don't know how to find it.

There are two dipsticks for the MBZ, graduated in mm. One is flat, one is "twisted" Depending on model, one may work better than the other (or not at all) . Both work in my Cl65, the flat one doesn't hang up as much. At the proper "resting" oil level, it should be 120mm on the stick. Like some - I don't trust sensors, (or dealers for that matter) and like to see it for real. My mechanic says the MBZ sensors are excellent, but it doesn't hurt to use the stick. Still looking for a source on one - will post when I find it.
On the dealer subject - tranny had gasket replaced by the dealer, came back 1 and a half qts overfilled. - pays to check

You can find the oil dipstick at any MB dealer. I can get with my parts lady later on this week and ask her for the P/N.