My 100,000 mile 1988 560SL is consuming/leaking over a quart a month. I know some of it is due to leaking due to my observation of the ground below the car. Would like to hear some experience/recommendations of the steps which should be taken to economically resolve the leaking/consuming problem. With all the experience out there I am certain there are more and less likely culprets. I recall reading that the valve cover gasket is the best place to start. Although not constant, I sometimes see white smoke coming from the exhaust.