When it comes to extra fees, car rental businesses can be among the worst offenders. In some cases, those extra fees and taxes can push the rental rate up by 30 to 40 per cent.

For instance, it costs more to have a child safety seat, satellite radio, insurance and emergency roadside assistance.

Consumer Reports compared the fees at nine big rental companies, including Enterprise, Hertz, Avis and Dollar.

"Car rental companies don't make it easy to find the charges on their website. But they certainly do a great job of loading on the fees when you return the car," said Lisa Lee Freeman of Consumer Reports ShopSmart.

If you add another driver, you can pay $13 to $30 more a day. If that second driver is under 25 years old the fee can jump to more than $100 a day.

Losing the key can cost you as much as $375. And be especially careful about picking up the car in one place and dropping it off in another.

"The lowest drop-off charge we found was $50, but believe it or not, in some cases Avis charges as much as $1,000 to drop off a car in another location," said Freeman.

At Avis, if you return a car even 30 minutes late, you'll be charged for nearly a full day's rental. Also, be sure to fill up the tank before you drop off the vehicle to avoid paying extra-high prices for gas.

Rental companies charge for refuelling. For example, Budget tacks on another $14. Before you leave home, make sure you check your auto-insurance policy and credit-card protection so you know whether you really need to pay for car rental insurance. You may already be covered.

Make sure you read the fine print. Claiming you didn't know about fees is no defence. If you smoke in a smoke-free car you could pay up to $250 in cleaning fees. Make sure your four-legged friends don't shed in your rental car because that can cost you too.

Finally, it's always a good deal to pay with a credit card. That way you can dispute inaccurate charges.

With a report from CTV British Columbia's Lynda Steele