what is so special about mr grangers car?

It is exactly like Uncle Hammer's car.

Sorry, wrong chapter. In this instance we have the symbolism of mr Granger's car..... first of all it is a show of wealth, second it is a possession, but most importantly it is a symbol of control. He controls his own movements and therefore his life; the others...... do not have this luxury, as in many cases he controls them too (the Logans).

it was gray, shinny, and like uncles hammer car.

It shows wealth, possession but mostly control and he controls his life.