I'm on my second Prius! Love, love, love them. I average about 51 mpg, and find that the best mileage is obtained driving in hilly areas with no heat on. The air conditioning doesn't affect the gas mileage, but heating the car does since the heat comes from the gas powered engine, not the electric. I owned the first Prius for six years, and the only repair/expense was to replace tires and the regular battery....the one that starts the car. We get excellent service at our dealership too. There's plenty of room for four adults, and we have squeezed five in, and never have to pull the front seats forward. Can't say enough good things about it!