A friend told me, her boy friend spent 50 dollars more to his car insurance, then he can use his car insurance to cover car rental insurance.
Credit card company has an insurance company providing car rental (LOSS and DAMAGE Waiver), go to your credit card site (then car insurance site) and read the terms, find out what is covered and what is not. I think you cannot use it to rent expensive cars. Also ask your credit card car insurance provider what to do if there is accident.
Good luck LZ.