Oak Essence

Has anyone ever used liquid oak essence in secondary fermentation? Is it as potent as vanilla extract where you really only need to use an once or so to get the full flavor in a five gallon batch?

I used some at bottling with an ale not long ago. I used 1/2 teaspoon in a few bottles and 1 teaspoon in a few others. The bottles were 750 ml. I believe the equivalent for the full teaspoon bottles would be close to 4 ounces for a 5 gallon batch. The flavor was not overbearing at all in either, but you could definitely taste it.

I might do it again at some point with the rest of the bottle I have.

I don't know if this helps, but it's my experience with oak essence.