Octane Display and Disclosure Act of 1991

Octane Display and Disclosure Act of 1991 - Amends the Petroleum Marketing Practices Act to require certification and posting for all liquid automotive fuels (currently, automotive gasolines).

Authorizes States or local governments to provide for any investigative or enforcement action, remedy, or penalty permitted under such Act. Revises Federal Trade Commission enforcement provisions regarding acts or practices constituting violations of the Federal Trade Commission Act. Changes the Environmental Protection Agency's authority to conduct field testing of the octane rating of automotive fuels from mandatory to discretionary.

Directs the Administrator of the Environmental Protection Agency to carry out a study to determine whether, and if so, how, the anti-knock characteristics of nonliquid fuels usable as motor vehicle fuels can be determined.

Directs the Secretary of Energy to study the feasibility and desirability of using dye to: (1) differentiate automotive fuels with different fuel ratings so that the rating can be determined by its color; and (2) identify transportation fuels required by law for clean air or other environmental benefits.

Directs the Federal Trade Commission to study the need for, and the desirability of, having a uniform national label on devices used to dispense automotive fuel to consumers that would consolidate information required to be posted on such devices.

Requires reports to the Congress on the studies carried out under this Act within one year.