Hi, Im considering changing from the standard size wheel to the next size up! If they fit in the arches, will i get better MPG? Also I read here that "Add this to a car where servicing costs are free for three years" Yet my Matiz isn't 3 years old, it had a 30,000m service having oil & air filter and engine oil, YET cost me £285 !!!!! what's going on here then?