The peeled/prepared garlic in oil (whether whole cloves or chopped or minced) has to be irradiated or contain preservatives and other stuff to sterilize it and retard decomposition. Thus, it doesn't have the same "impact" as freshly prepared.
Occasionally, you can find jars of pre-peeled garlic "buds" that haven't been treated with anything. These are pretty much the same as fresh garlic but will rot faster than a politicians reputation, so take care and discard them if you sense any degradation, mold or non-garlic aroma from them.
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