14 C.F.R. § 23.1551 Oil quantity indicator.
Title 14 - Aeronautics and Space
Each oil quantity indicator must be marked in sufficient increments to indicate readily and accurately the quantity of oil.
Title 14: Aeronautics and Space
PART 23—AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES
Subpart G—Operating Limitations and Information
Markings And Placards
§ 23.1551 Oil quantity indicator.