Another thought, 6.5+35=41.5 litres, not 45 litres as Toyota's spec. stated. I guess you might be able to squeeze in a few more but you're risking gasoline spillage. Obviously that's another safeguard measure implemented by Toyota. Fault them for not telling us, not for implementing the safeguard. I remember my old Honda Civic stated gas tank volume of 35 litres max. but everytime I fill-up it could only take 32. That translated to 400km/250miles range on 30 mpg average all city driving. We should be VERY SATISFIED with the Prius range of ~600 miles. Anyway, I've been thinking of not topping up the gas tank everytime. Just fill 13 litres every time giving me about 300km range good for one whole week of driving. That'll lighten up the car for about 22 x 0.7 kg/L density = 15.4 kg = 34 lbs. I don't know if that's gonna help the mpg but I'm trying to time my gas filling day to fall to every Tuesday late evening. Years of experience tells me that's when the gas prices are lowest.