I have a '94 SL500 5L and noticed about a year ago, when traveling across the Smoky Mountains, that my oil pressure dropped to 0 at the higher altitude (4,000 feetish) and the engine temperature was about at 180. If I dropped down to 2nd and kept the revs above about 3,000 the oil pressure would be OK. It didn't help when coasting down hill, but eventually the enginge temperature would drop some and the problem would go away. I noticed it again later, when not in the mountains, when I would use 2nd for a short period of time and then go back to 3rd or Drive. It happened again this past weekend going back over the mountains, and dropping to 2nd seemed to be the cure until I got back to somehwhat lower engine temps. Any thoughts would be appreciated. Thanks.