During WW2 America turned to the railroads to transport oil after U-boats closed our shipping lanes in 1942-43. Unit trains of 8,000 gal. tank cars expedited oil from mid-continent to the east coast.

8,000 gal. tank cars like this 1/48 (O scale) model were found all over the US, and even sent overseas to support the war effort. It will work great in a 1/48 diorama c. 1916 - 1950s.

http://railroadmodeling.kitmaker.net/review/7367