I bought a 1980 450SL in 2005 and have driven it periodically over the last ten years.

It has had a very noticeable oil leak for years, enough to top off occasionally, but not enough to cause low oil levels in a short period of time. I use Mobil 1 full synthetic, which I suspect contributes to leaks.

This spring, I started the car for the first time since winter, and noticed smoke coming from the hood in front of the passenger seat. On investigation, I suspected a valve or valve seal issue. As the car idled, the smoke burned off, and was no longer noticeable.

Flash forward to this evening. I haven't driven or even started the car in months. I decided it would be good for car and tires to start and move a bit. I cranked it, and there was considerable white smoke. I opened the garage door and drove it into the driveway, and waited for the oil to burn off. It was thicker and lasted longer than before. I popped the hood and saw the smoke coming from the same area, I thought, near the top of the engine, but I didn't actually see leaking oil.

After a while, the smoke stopped. Temperature looked good, the engine sounded right. Resigning myself to a valve head job, I backed it into the garage ...

Then saw an approx. 12" diameter oil slick underneath where the car had been. I would estimate the oil volume to be several ounces. This happened in perhaps 10 minutes of idling. In the past, it took months to stain that large a spot on the garage floor, and I rarely saw oil drips on my driveway or elsewhere.

I looked under the car in the garage and saw perhaps an ounce of fresh oil under the oil pan, the corner toward the passenger side. It got dark and I stopped investigating for now.

Any theories? I would think the symptoms are related, but perhaps they are coincidental?