I used to own a old Benz and service it myself whenever possible. I wanted to add some grease to the wheel bearing one time, but stopped when I read in the workshop manual that using generic wheel bearing grease will destroy the wheel bearing because such grease is not compatible with Benz's factory packed grease. The manual went on to say mixing factory grease with generic grease might cause a chemical reaction that turns the combo grease into liquid that leaks out.
I just pulled apart the head set on my bike and noticed the bearings might do well with a little more grease. Can I use regular bearing grease from Autozone and just add it into whatever grease is on the bearing already? I have to ask to be sure after the enlightening experience thanks to Benz's technical writer.