16 C.F.R. § 259.1
The Guide in this part contains administrative interpretations of laws enforced by the Federal Trade Commission. Specifically, the Guide addresses the application of Section 5 of the FTC Act (15 U.S.C. 45 ) to the use of fuel economy information in advertising for new automobiles. This guidance provides the basis for voluntary compliance with the law by advertisers and endorsers. Practices inconsistent with this Guide may result in corrective action by the Commission under Section 5 if, after investigation, the Commission has reason to believe that the practices fall within the scope of conduct declared unlawful by the statute. The Guide sets forth the general principles that the Commission will use in such an investigation together with examples illustrating the application of those principles. The Guide does not purport to cover every possible use of fuel economy in advertising. Whether a particular advertisement is deceptive will depend on the specific advertisement at issue.
16 C.F.R. §259.1