If you’ve ever had to rent a car, you know that car rental companies love to sell insurance on their cars. They’ll often ask whether you’d like just the basic coverage or additional coverage at the counter even after you’ve already declined both when making your reservation. After all, it’s one of their big profit centers.

Of course, when you’re busy traveling is one of the times when you’re least in the proper state of mind to make a good decision about this sort of thing. You may also not want to spend too much time thinking it over with a long line of fellow travelers behind you rushing to get somewhere. An NAIC study showed that 42% of rental car consumers  were “either thoroughly confused or had only a rough idea about insurance.” Some people skip it without thinking to save money while others buy it just to be safe. So is it a good idea?

Well, what could happen if you don’t buy the insurance? The worst case is that you get into a car accident, which is exactly what happened to me last week (on Fri the 13th of course) after declining the coverage. (Don’t worry, no one got hurt.) Here is what I learned from this experience:

Rent the car using a credit card with rental car insurance. Since I turned down the loss damage waiver, the damage to the car was charged to my insurance company and I was responsible for my $500 deductible. Fortunately, I had made sure to rent the car with a credit card that offered rental car insurance that covered the deductible so I don’t have to pay anything out of pocket. I have to admit that this was one of the moments when I really appreciated credit cards. After all, the coverage cost me absolutely nothing except  the time it took to make that phone call. Just be sure that you contact them right away because there are time limits (usually around 45 days) after the accident in which you have to make a claim.

Your personal auto insurance is generally primary for any liability. That means the car rental company will probably charge your personal auto insurance before the rental insurance kicks in. If you have sufficient personal liability insurance (and I hope you do), the rental car insurance won’t be necessary at all. Even if you don’t, the rental car company has to provide a minimum level of liability insurance automatically so you’re only purchasing supplemental coverage above that.

For me, those two facts justify not purchasing the rental car insurance. The only advantage I would have had is that I wouldn’t have had to make a claim on my insurance at all if I had backed into a parking garage post or something like that since the loss damage waiver would have covered the damage to the car and I wouldn’t have needed any liability coverage. In those very limited circumstances, I wouldn’t have to worry about my insurance rates going up (the worst part of this whole thing) but the odds of that happening just don’t make it worth the cost for me.

So when should you purchase the insurance? I can think of a couple of situations. One is if you don’t have car insurance (like my carless NYC friends). The other is if your rental falls under some of the exceptions to your personal auto insurance coverage of rental cars. For example, mine doesn’t cover long term rentals or business use if it’s rented under the company name so check the details of your insurance coverage. Oh, and one more thing: you might want to think twice about skipping the insurance if you’re traveling on Fri the 13th!