Unit volume conversions

I am creating this page in hopes of adding a few less know conversion values commonly found in oil field applications. Refering to Wikipedia link [http://en.wikipedia.org/wiki/Bbl|http://en.wikipedia.org/wiki/Bbl]

My intrest would be to add the unit of (bbl) in value of 42 gallons US oil per bbl US. It may be that it may needs to bbl ... defined with the measure oil bbls US..etc.