CLEVELAND -- If you're thinking of renting a car for your late summer vacation but you want to share the driving responsibilities with a spouse or someone else, you might want to think twice.

According to On Your Side Troubleshooter Chris Caswell in this week's edition of Betcha Didn't Know, you'll pay a fee to add a name to the driving list.

Fees for a second driver on any rental car can really add up, so it may be worth it to have a designated driver on vacation.

When you go to rent a car, it pays to appoint one person to drive it. If you try to share the wheel, you're likely to face extra charges.

"When I'm traveling with my family, I find I'm annoyed by it," one driver said.

Consumer Reports checked policies at the eight largest rental companies. The fees for a second driver are all over the lot.

Avis charges one of the highest fees for second drivers -- up to $25 a day. Some companies charge a lot less -- maybe only $4 or $5 a day. But in most cities, with most companies, you're going to have to pay for a second driver.

In most cases, Hertz will make you pay the extra fee even if the second driver is your spouse. So will Alamo and National.

If the second driver is under 25, money isn't the only obstacle.

Some companies will simply not let a driver younger than 25 drive their cars. In other cases, you're going to have to pay a huge surcharge -- up to $25 a day for a younger driver.

So before you rent, check the company's policy. You'll probably find that it pays to have just one driver.

Some rental companies will waive the second driver fee if the second driver is your spouse. However, it helps to have the same last name. If you don't, the company may ask for your marriage license to make sure that you're really married.