J12 is one of my favorite Mangos. It has a deep, rich flavor that is unique, yet reminiscent of its parent Julie. Early in its ripening stages I find it has a strong citrus flavor with a potent combination of sweet and tart. Late in its ripening stages it can be sweet like syrup.
As far as the "gasoline" flavor some are referring to, most of the fruit from my tree have only a slight nuance of this note. Some none of it, and a few it is profound.
All being said, it is excellent to my palate. My sons favorite mango, and the best I've had this season.