Here in Europe, the Prius has a 1800cc engine faring about 98hp and demands 98RON gas; I have instructed ny wife to use strictly 98RON gas in the Toyota.
Early Piuses had a 1500cc engine which proved quite below expectations; that same engine is now fitted to the Toyota Yaris Hybrid (picture below)
Definitely a tiny car by US standards but it will sit 5 (tight) and you can park her anywhere... literally !
Anyway, last Sunday we drove to my sis-in-law's, and at a more or less steady 90Km/h (55mph) we averaged 3.8 liters/100 Km... that's 62mpg...