I have noticed that if I drive my 380SL ('86 560 engine) around for maybe an hour or so and come home there is a small oil drip on driveway. I have not been to worried about this until this week when I drove for about 150 miles at highway speeds and when I got home later on I noticed a large spot of oil about 8 inches in dia. Any suggestions as to why the difference and what it could be?

Thanks much.