I just won 150 uncleaned coins, which for the most part are pretty crusty. I am going to put most of them in a jar of olive oil for at least a year and check how they look. My goal is to see how long they have to sit in the oil until they are clean, without me scrubbing...or if it is even possible. Some will probably clean pretty easily, others not so much. I will change the olive oil as needed, but will not otherwise disturb the coins.
The longest I have left coins in olive oil is only a few months with mediocre results, so I figured I would give this a shot.