I have been using this type of units for about 15 years. I finally modified my Mityvac (see link below) and I would not be happier. The speed of removing the oil is much faster and I also got a little more oil out than putting a small tube into the dipstick tube.

http://www.benzworld.org/forums/w210-e-class/1434467-kajtek1-mercedes-way-sucking-oil.html#post3392043

This can be bought from Sears, Amazon, and various other places. Do get the one that has over 8 liters of capacity.