Final answer:
It's true that at high altitudes, the grades of octane for gasoline are reduced, due to lower atmospheric pressure and less oxygen available for efficient fuel combustion.
Step-by-step explanation:
The statement is true. When driving at high altitudes, the grades of octane for gasoline are indeed reduced compared to the grade of octane available from gasoline retailers located at sea level. The reason for this is that an increase in altitude results in a decrease in atmospheric pressure, which affects how gasoline combusts in an engine. Because there's less oxygen available for the fuel to burn efficiently (a condition known as hypoxia), engines can run on lower octane fuel without the risk of knocking that can occur at lower altitudes with higher atmospheric pressure.