Which of the following statements is not true?

Driving at high speeds results in tire wear and poor gasoline mileage. Vary your speed from time to time to prevent monotony and road hypnosis. You are not required to drive at the maximum speed limit. However, you should not drive so slowly that you interrupt the flow of traffic.

• Driving at high speeds can cause tire wear.
• Constantly driving at the same speed causes monotony and road hypnosis.
• Driving at high speeds results in poor gasoline mileage.
• You may not drive below the posted speed limit.