Wash12, think of incorporating as though you were buying an insurance policy - insurance against losing something you have in a lawsuit. What assets do you have, what risks do you have. E.g. if you live in litigious cold Massachusetts and dont have floor heat, incorporate, and do it fast! If you are in Arkansas, dont have a McMansion and a fishing boat, run a very tight operation, and your courts are business friendly, buy insurance.
JGinther is correct - incorporating reduces your liability. (reduces, does not eliminate).
Mike is also correct - in many cases, simply increasing your liability limits on your insurance is usually cheaper and can make more business sense.
Both have costs, initial and ongoing.
I'll also go out on a limb here and say that since LLC's have significantly reduced the costs of being a corporation, the majority of car washes are becoming an LLC. If you did a survey I think that would be the majority.