If your business is a corporation -- even a one-person corporation -- it's legally a separate individual. Your money and the corporation's account are two separate pools. If you want your company to have title to the car, you have to buy it with business funds or have the corporation take out the loan. The title goes in the business's name.
It's perfectly legal to drive a company car on personal business. It's also taxable: The use of a company car is a fringe benefit, and your corporation has to report the equivalent cash value on your W-2. There are still advantages to driving a corporation-owned car, though. The insurance premiums are often lower, and the company may get a better interest rate on a loan than you would.
