Answer: Gasoline
Roosevelt’s order was to go into effect on December 1 and its real reason was to help conserve rubber needed for the war effort.
“President Roosevelt served notice tonight that, Congressional upheavals and sectional objections notwithstanding, the government must and would begin the nationwide rationing of gasoline to conserve rubber on Dec. 1, as scheduled.”
Source: The New York Times report on the controversial order.
Read more about Roosevelt and World War II in Don’t Know Much About® History and Don’t Know Much About® the American Presidents.