Ricky has both expressed love and hate for the vehicle, and at one point he threatened to burn it up when it appeared he didn't need it anymore, but it turned out that his circumstances changed abruptly and he had to use it for living quarters once again.
Since it was used as Ricky's 'home' most of the time, he used it for almost all house-related purposes, including sleeping, for a cooking surface, growing dope in, and even showering. Typically, when not in motion, the shitmobile is littered with all manner of personal effects and debris, which is later cleared off with the 'clearing stick' when it is needed for travel.
It appears in many episodes and although it's history is most known as a car that was passed on from Julian's grandmother, to Julian to Ricky (where it was damaged) in the christmas special it shows the car door being ripped off thus creating a new possible solution to how the door was ripped off.
The shitmobile's transmission does not operate according to design: according to Ricky, third gear is normally used for driving, as the "drive" gear causes the car to go in reverse. Neutral parks the car, while reverse puts it in second gear. [Source: S03E06, "Where in the Fuck is Randy's Barbeque?"]