Cal. Bus. & Prof. Code § 13472

When a sign is used in addition to a price indicator, as defined in Section 13470, and if the same grade of motor vehicle fuel is sold at a different price from any other dispenser on the same premises, it shall be unlawful to display the sign on a dispenser unless a sign with price numerals of equal size is displayed upon each dispenser from which the same grade of motor vehicle fuel is dispensed at higher prices.