Is it necessary to buy rental car insurance even though i have my car insurance policy with me?

There are things for which you would be charged with a rental car but your auto policy would not cover. Your coverage extends only for instances where you are legally liable, which leaves out a lot. For instance, if a vehicle is damaged by a hit and run, your personal auto policy would generally not extend coverage but you would still be responsible for the damage. Theft gets tricky too. They also charge for down time, for which your personal auto policy would not pay. I recommend renting your vehicle with a good credit card. American Express and Discovery tend to extend some coverage for rental cars, which does help fill in some of these gaps.

Do you have a "gold" credit card? Rental insurance covers your collision and comprehensive deductible. So will most "gold" credit cards.