Some helpful tips from Greg Ellifritz at Active Response Training, excerpted here:
3) The situation changes, however, once the rioters attack you or your vehicle. With your vehicle surrounded in a manner that you can’t escape and your attackers being trying to burn your car, flip it over, or drag you out, it is reasonable to assume that you will suffer serious injury or death. That’s when you can start striking people with your car. Don’t get out and shoot. You will quickly be overwhelmed and your gun will be taken from you. Instead, accelerate steadily and forcefully, driving away from the surrounding rioters. Steady movement is the key. Hitting folks too hard can disable your vehicle. As John suggests, use your vehicle to push people out of the way rather than striking them...
As they say on the real blogs, read the whole thing.
Hat tips: BadBlue Guns and Gun Free Zone.