History of the 4BBL Abbreviation

By Brandon Flannery

We’ve all seen and written “4BBL” a hundred times when talking about carburetors and throttle bodies. At one time or another most of us have wondered about the mysterious second letter B. Obviously, we know it stands for “barrel”, but why the extra B?

I have a theory.

The abbreviation bbl is widely accepted as a unit of measurement for barrels of oil. Oil companies report their production on the Stock Exchange in terms of volume in the units of bbl. Today, the government and military also use bbl for the abbreviation of the word barrel in relation to a unit of measurement for fluids.

That unit is a 42-gallon barrel of oil, officially agreed upon and adopted in 1872 by the Petroleum Producers Association. Prior to this standardization, oil was shipped in a wide range of barrel sizes. In 1859, the nation’s first oil boom in Pennsylvania caused a scramble to ship this hot new commodity, and an array of repurposed barrels of varying sizes were used. The need for standardization came to resolve buyer distrust in correct quantities for money spent.

The standard 42-gallon wine tierce was agreed upon over the 40-gallon whiskey barrel to accommodate an extra two gallons, in the favor of the buyer, to compensate for evaporation and spillage during shipping. When filled with oil, the tierces weighed 300 pounds, a weight that was just large enough for a man to move around by himself. Additionally, 20 of them fit on a barge or railroad flat car.


One leading theory of the “bbl” is linked to Standard Oil’s legendary blue barrels, some of the first to be shipped in great quantities after the oil industry’s adoption of the 42-gallon size.

One popular explanation of the “bbl” is attributed to the “Blue Barrel” theory of the Standard Oil Co. Inc., established by John D. Rockefeller. In the mid-to-late 1800s, Pennsylvania experienced a large oil boom and shipped it out all over the country by rail. In those days, kerosene was far more popular than gasoline. Gasoline was shipped in barrels painted red, while kerosene was shipped in barrels painted blue. The theory is that as the new industry standard of 42 gallons was implemented, the vast amount of “blue barrels” being shipped came with a ledger designation of “bbl” to differentiate the volume. As the practice of painting the barrels faded off and gasoline’s popularity rose, the abbreviation stuck.

This theory works well for most people. However, Ida Tarbell’s 1904 Standard Oil Company history states the abbreviation of “bbl” had been in use long before the 1859 birth of the U.S. petroleum industry. In fact, ship manifests from the very early 1800s listed quantities of honey, rum and whale oil shipped in units of “bbl.” Speculation for this includes that it may have been to indicate a plural quantity – 1bl and 2bbl, for example. Or, a more plausible guess is that it might have been to eliminate confusion with the “bl” used for a bale.

After my research, I would like to add another theory I can’t prove without a time machine, but makes more sense. The style of barrel used since the beginning of shipping things in barrels was a water-tight design made from curved staves of wood held together with metal hoops. They were wider in the middle. That portion of the vessel is known as the “bilge,” and this design also allowed the barrels to be rolled easily. They were known as “bilge barrels”.

In 1909, Frederick A. Prahl filed for a patent for a “Knockdown Bilge Barrel,” and in 1910, Joseph H. LaFave filed a patent for a metal bilge barrel, a new design for the popular “liquid-tight bilge barrels,” as he put it in his patent application. My theory is that these were verbally referred to as “bilge barrels,” and this would account for the usage of the second B long before the blue barrels of Standard Oil, as well as differentiate it from other styles of vessels.

In any event, the short answer is bbl is the US standard abbreviation for the word barrel, and it was implemented into the automotive industry when identifying the number of barrels within a carburetor.