it's fuel tank has a bladder type of device which expands and contracts. So the quantity of fuel filled on every fill may differ a little bit. While getting it filled tell the guy to not fill it at full speed and also stop where the machine stops.
Regarding ground clearance I have owned a 2008 S 10th 1.5 liter and now have a 2010 L 1.8 liter. the ground clearance of 1.8 is better than 1.5 though it looks lower. I got 1" packing in my 2008 prius but never needed any extra packing for 2010 it does not hit where 2008 used to hit.
Have changed the rims on my 2010 to Mark-II 16" rims with Michline Energy Saver 205-55/R16. The looks have improved a lot while maintaining the comfort of drive. Didn't go for 17" as they make the ride quite rough. Will post the pics after getting it washed, is quite dirty as you know the road condition in Islamabad now a days is pathetic. I was getting around 23 km/L average but after changing the tires it has dropped to 20 km/L. But am happy as it is still hell of an average on full time AC.