I changed my oil for the first time on my recently purchased 91 300E MB 4Matic. I jacked it up with the MB pole type jack put a Jack Stand under the rubber bumper and then did the other side.

To make a long story short the car fell and not exactly on the bumps where the jack stand were. The jack was dis-abled also. I used another standard jack on the frame to lift the car and put things in place.

In order to be safe and potentialy save your life, don't go under the car using just the jack, use Jack Stands. If you jack up both sides it appears the jack is not safe. I highly recommend putting the full load of the car on the Jack Stands and REMOVE the JACK. Rock the car with your body to be sure the Jack Stands are stable.

I know this is common sense, but I believe the problem occured because I left the Jack in place and I am a newbie to MB pole jacks.