Flow rates from the oi leaks were generally expressed in barrels per day (bpd) and sometimes in gallons per day (gpd). So I went and took a look at American volume units, and holy cow, those are a real mess.
A barrel is... well, it depends: oil barrel - 42 gallons; other barrels may vary. But 42 is not basis 12, nor 2, neither 10: it's just a number pulled out of god-knows-where.
And a gallon? Not related to cubic foot, neither inch - 231 cu. in, what is that?
Same for the barrel, no relation to cubic yard.
Not only Americans use units which are more or less closely equivalent to the British ones (before the tidying up of 1824), but apparently every field of technology over there has its own units.
Yes, that may be because they are more free. But the freedom to complicate things unnecessarily is something I can renounce, really.