I finally found the oil leak on my 2000 G500. The "upper oil pan" had a hole in it the size of a quarter that had been welded up. That apparantly leaked so they used JB Weld. That worked for most of the 1.5 years I have owned it. The hole was on the vertical next to the oil level sensor.
I have no idea how it got there. There is a frame member nearby. I know the rear door was replaced, maybe it got whacked in the rear and broke a motor mount. No other damage anywhere on the car.
I tried to weld up the weld but it was too contaminated with oil/crud. The good news is that the dealer quoted about $260 for the part. It is a big aluminum casting.
Oh well its just money.