As a businessowner, you need the same kinds of insurance coverages for the car you use in your business as you do for a car used for personal travel -- liability, collision and comprehensive, medical payments (known as personal injury protection in some states) and coverage for uninsured motorists. In fact, many business people use the same vehicle for both business and pleasure. If the vehicle is owned by the business, make sure the name of the business appears on the policy as the "principal insured" rather than your name. This will avoid possible confusion in the event that you need to file a claim or a claim is filed against you.
Whether you need to buy a business auto insurance policy will depend on the kind of driving you do. A good insurance agent will ask you many details about how you use vehicles in your business, who will be driving them and whether employees, if you have them, are likely to be driving their own cars for your business.
While the major coverages are the same, a business auto policy differs from a personal auto policy in many technical respects. Ask your insurance agent to explain all the differences and options.
If you have a personal umbrella liability policy, there's generally an exclusion for business-related liability. Make sure you have sufficient auto liability coverage.