I just gave my new Prius a 200 mile break-in run to Minneapolis. It was at night (lights on), in rain (resistance), 36F (engine ran to heat cab) and without wind of any consequence. Drove 55 for the first 30 miles (rolling hills) and averaged 52 mpg, beating the epa rating. Drove the next 170 miles changing speed at 30 minute intervals per dealer's recommendation running 55, 60, 65 and 70. Averaged 47.2 mpg. As far as I'm concerned, the
50 mpg rating at highways speeds (55 when established) is accurate. Navigation system brought me precisely to my destination.