I am a Car Dealer and a Mercedes mechanic gave this MOST sucessful tip.
Drain your oil if not recently changed! Re-fill with good oil BUT substitute with one quart of transmission fluid.Dex3 is fine.
You might be amazed.This works if it's just the "O" ring around the lifter and or there is some crusting around any oil holes.
A cheap fix if it works.Also make sure that you either drive the car for a length of time or let it idle for a LONG time afterwards.
Drive the car at least a month to let all that crude dissolve.
I have cured at least 20 cars like this.As a added bonus your car will feel awsome and smooth.

Regards.
Rafiqi.