I was in the same boat as you are. Just purchased my 300 and got a big suprise when the oil light came on after a couple weeks of use. My car was around 76k miles also. Mechanic said it was the valve guide seals and replaced them. The parts are so cheap . . . I mean inexpensive. He said that the first time they need to be changed is around 75k miles. He also stated that MB knows they are a problem and has changed them somewhat so that now they will last around 100k miles, (after changing them the first time). Haven't used a drop of extra oil since.