In short, there are four different kinds of basic rates charged by car rental companies: daily rates with all mileage billed extra; daily rates with a limited number of free miles per day; daily rates with unlimited mileage; and a rate that has free mileage over an extended period of time. Naturally, all rental car agencies charge different rates based on the size and style of the vehicle, with most firms renting economy, compact, intermediate and deluxe cars. Tip--renting a car for a full week is often cheaper than renting for five days.

An important consideration when renting a car is the length of time you will be needing the vehicle. If it's less than a week, you'll probably find lower rates with a major, national company like Alamo, Avis, Budget, Dollar, Enterprise, Hertz or Thrifty. For rentals of a week or more, you may get better prices from local companies, especially auto dealers. Be wary of local companies if you plan to drive quite a few miles; if you have a break down or an accident, they usually lack the services and support of the major companies.

The basic rate you see advertised in big print in magazine, newspaper and television ads, are only the tip of the iceberg when it comes to car rental costs. Surcharges (usually in the form of taxes) are sometimes the result of greedy cities, states, airports or the rental car company itself. Whoever is at fault, these nasty little add-ons can boost your total rate by as much as 50%. Sales taxes, airport taxes, concession fees, vehicle leasing fees, and drop-off fees often don't show up when you're quoted a base rate for renting a car. Renters sometimes find themselves charged other miscellaneous fees, such as a bill for the shuttle that brings them from the airport to the car rental parking lot, or an expensive fee for additional drivers.

The best remedy to reduce "contract shock" is to use travel agents, booking services and Web sites that disclose all fees in advance. Some companies are taking away the mystery surrounding car rental rates by offering "total pricing" for their cars. Your total rental cost will be calculated prior to making the reservation, guaranteed to be within one percent of the actual rate.

An additional expense of renting a car is the insurance the company sells. The term "insurance," by the way, is a misnomer since rental car companies aren't licensed to sell insurance. What they are selling are waivers, so you're not on the hook for any damage caused in an accident.

The three kinds of waivers "encouraged" by the major car rental agencies are as follows: physical damage waivers that cover any harm done to the rental car; liability waivers that cover any harm you do to others and their property while in the car; loss damage waivers that cover theft, vandalism and loss of use, which covers the rental fees the company might lose while the car is being repaired.

Your personal car insurance might cover these occurrences, but they might not! The only way to know for sure is to call your auto insurer and ask about insurance coverage on rentals. Even then, your personal insurance may not cover rentals abroad, or certain vehicles such as SUVs, trucks, vans and campers. Do a little research now, save yourself some money later.

When it comes to fueling plans you also have a variety of options. You can: prepay for a tank of gas when you rent the car (favored by the car agencies since you probably won't use a full tank); the worst deal is simply turning the car back in empty since you could be charged about $5 a gallon plus a re-filling fee. The best choice--pay for only the gas you do use. Make sure the tank is topped off when you pick up the car, and leave yourself enough time to find reasonably-priced gas near the airport on the day you leave so you can re-fill the car yourself.

Always comparison shop, even on the Web. Major car rental companies often offer Web-only discounts--take advantage of them whenever possible. Check the Car Rental Center, as well as the individual car rental sites. Ask about discounts for membership in national organizations (like AAA or AARP) or special rates for frequent-flier programs or credit card plans you may enjoy. They frequently offer good deals on car rentals.

Whether you book online or by phone, you can usually get a much better price by renting well in advance of your trip, especially if you reserve during a low travel season and travel in a high season. Make sure to ask the agent about restrictions, additional fees and insurance costs.

Finally, be careful to coordinate pick-up and return times so as not to be charged for an extra day. Best wishes for safe traveling.

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