Points are allocated depending on the location, model and part of the car that is 'Jizzed' onto. Bonus points are awarded for occupants being inside the car at the point of ejaculation.
The ultimate top scorer during a game of 'Jizzcar' is to 'jizz' onto the windscreen of a poilce car at a red light, with a policeman in the driving seat and a criminal in the back. The rarity of this event makes it legendary and known as the 'MEGAJIZZ'. Few have achieved this.
A time bonus may also be given, for example, at a red light, you have very little time to work with and so achieve a higher score.
Open windows are also very highly scored. if you are able to 'Jizz' onto a confused driver, you are very highly skilled at 'Jizzcar'.