NEW YORK (MainStreet) — It is one kind of Russian roulette nearly all of us play.

You would not empty a revolver of all but one bullet, spin the cylinder and aim the barrel at your head.

But most of do an equivalent at the rental car counter when the question is popped about whether you want the optional insurance.

Do you need it? Back into a craggy high desert boulder in Taos, NM and, odds are, the costs will top $5,000 to replace the rear bumper and maybe a fender. And that is a trivial accident. Get into something serious and the vehicle will be totaled and now we are talking real money.

But insurance protection bought at the car rental company is not cheap, either.

At Enterprise Rental Car the going rate for CDW (Collision Damage Waiver) bought online when booking is $11 per day. Many other companies charge more. $20 per day is not unheard of.

At least in Phoenix on weekend days, a Chevy Spark can be rented for $33 per day.

That means the insurance is a big piece of the final price.

Should you say no?

"It is common to get a high-pressure sales pitch for CDW at the rental counter," said John Wetmore, producer of "Perils for Pedestrians" television. "Since I know my facts ahead of time, I can turn down the CDW with confidence."

That's because Wetmore believes he is amply covered by his personal car insurance and also by coverage provided by a credit card.

Is he right? Probably because he has looked into what coverage he has.

The rest of us may be playing a version of Russian roulette, however. In a poll conducted by the National Association of Insurance Commissioners, 42% of us said we were "thoroughly confused or had only a rough idea about insurance coverage when renting a car."

Ask the experts and they say that many of us indeed are utterly mistaken. We believe we have plenty of coverage without buying the rental car company's -- but we may be wrong.

Have an American Express card, for instance, and when it is used to pay for the rental, it covers up to $50,000 in damage or theft. But, note, this is secondary insurance - it kicks in after primary insurance, typically car insurance on a personally owned vehicle and so an accident in a rental car may well result in increased personal car insurance rates.

Worse: the Amex insurance does not cover luxury vehicles, SUVs and pickup trucks. If Enterprise is out of Sparks and you are upgraded to a Chevy Tahoe, guess what: that Amex insurance you had been counting on is not applicable.

Visa, Mastercard and Discover all also have exclusions.

Entire countries may be excluded. At American Express, Ireland, Australia, New Zealand, Italy and Israel are excluded for most cards.

Also there may be odd exclusions. Some cards exclude anything that happens on a dirt or gravel road (meaning don't drive in New Mexico or Vermont where pavement is the exception). Nobody told you? Tough luck. The exclusion was noted in the fine print riders we all toss in a drawer unread as they arrive.

The good news: in most cases, personal automobile insurance offers at least some coverage for rental cars but there are devils in the details and, to be sure, experts urge travelers to go over the coverage with their agent or a representative of the insurer before saying no to CDW coverage.

What about liability coverage? CDW only applies to damage to the rented vehicle. Liability applies to everybody else involved in the accident and costs can head skyward. Generally protections offered by credit card companies do not apply.

Buy liability from a rental car company and it generally runs around $10 and more per day - but, again, if you already have good coverage on a personal vehicle, it may provide all the protection you need.

But you still may not want to use your own insurance, said Laura Adams, a senior insurance analyst a

"If you have a high deductible on your insurance policy, you may want to take the coverage offered by the rental car company so you wouldn't have to pay the deductible," she said.

Add it up and do smart travelers buy insurance from rental car companies? Generally not if you have a credit card that provides some coverage and if you also have personal automobile insurance.

Is that playing Russian roulette? Indeed, and that is why savvy business travelers, who can stick an employer or client with the tab, usually buy all the insurances, because the good news about having all the coverage is that it ends conversation when it is time to turn the car in.

The clerk alleges that there is hail damage to the roof, or a door was keyed, or there's a crack in the windshield? If you bought the insurance that is that and you will be on your way swiftly and without haggling.

That's worth something. Is it worth $20 and up per day for coverage from the rental car company? That's your call.

--Written by Robert McGarvey for MainStreet