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The car rental industry has made an art out of the low-advertised-price scam, promoting a bargain rate that neglects to mention mandatory extras. Rent a car at an airport and you may be hit by a truly amazing stack of additional fees.

Besides the rental itself, you could be charged for the airport concession, the rental facility, and even the car’s registration. You may find charges for a local civic improvement, a juiced-up local sales tax, and other surcharges, including one levied on frequent fliers.

Those don’t even touch the optional extras: insurance, gasoline, additional driver, child seat, toll transponder, and navigation system.

Drivers under 25 may pay a much higher rate, face a large-dollar hold on their credit card, or not be able to rent at all. A possible solution for these younger drivers is a car-sharing organization like Zipcar (see below).

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You can ply these shark-infested waters with minimal danger if you’re willing to plan ahead. It can be a chore, but worth it in the end. For instance, you may find that renting the smallest car isn’t the best choice. Sometimes the rate for a midsized car is lower than for a subcompact from the same company—and it is likely more comfortable and safer.

When it comes to securing a rental car, comparison shopping is vital, and shopping online is the easiest way to go. Use a travel site like Orbitz, Kayak, or Expedia; a dedicated site like Carrentals.com; or simply Google “cheap car rental” and the name of the city you’re visiting.

We recently checked out prices for renting a Toyota Corolla for eight days, spanning a holiday weekend, from Chicago’s O’Hare International Airport. The 12 quotes produced by Orbitz ranged from $274 (Ace) to $615 (National), not including those pesky extra fees. With those, the rentals actually ranged from $404 to $897. The median quote, including taxes, was about $500.

Another choice you’ll see is to pre-pay with your booking or pay the day of pickup. Pre-paying can net a big discount, but check the cancellation terms. You want to be able to back out painlessly if your plans change—or you find a better deal.

Don’t be afraid to check out smaller car-rental names like Ace, Advantage, Fox, and Payless. Local and regional agencies can charge 20 to 50 percent less than the big chains, even if, as in the case of Payless, they’re affiliated with one of the majors. It might be a good idea to check local—and recent—online reviews on the smaller players, though. Service quality can vary a great deal.

Skip the airport

You might get a big break, perhaps as much as 50 percent off, by renting downtown, or in a suburb if you’re headed for one, rather than grabbing a car at the airport.

If you can avail yourself of a cheap shuttle, train ride, or cab trip to your hotel, all the better, especially if it allows you to skip the airport-rental queues and chaos.

One possible option, if you go for an off-airport deal, is to check out the cost of a one-way rental. This is where you drop the car off at the airport on the return leg. That may give you the best of both worlds.

Organizations like AAA and AARP offer cheap—or at least discounted—rental-car deals. AAA members may get perks such free use of a child seat. Costco and BJ’s also offer some great discounts. Costco, for instance, looks for deals that include an additional driver at no extra cost. American Express and numerous Visa and MasterCard offerings also offer car-rental discounts.

Weekend rates are often the cheapest, but you can also get good deals by renting at a weekly rate. But watch out for bigcharges if your plans change mid-trip and you end up returning your car sooner or later than you planned.

You may be charged for a full extra day if you’re as little as an hour late at drop-off. Some companies also charge you extra for dropping your car off too early. Your weekly-rate discount may be voided as well, sticking you with a far higher daily rental rate.

A rental company’s insurance offerings—Collision Damage Waiver (CDW), property-theft coverage, and so on—can add $10 to $30 per day if not more. If you have no alternative, you should spring for CDW. But your own car insurance may already cover you, so check that out ahead of time.

If you don’t carry collision coverage on your own car, though, you probably won’t have it on your rental, either.

American Express and many Visa and MasterCard programs also supply rental-car insurance, so long as you book using that card.

The rental clerk may say your own insurance doesn’t cover tires, glass, or days out of service. Check the fine print in your own auto and credit-card coverage before you leave home. And bring your insurance card with you, just in case.

When you inspect the car before picking it up, take close-up pictures with your smartphone, to prove that any minor damage or upholstery stains present were there at the start.

Turn these down

Child seat. If you need a child safety seat while traveling, bring your own rather than taking a chance on whatever the rental company has to offer. It may not be clean or easy to secure, and the fee—typically $10 a day—can quickly mount up.

Navigation. It may not be worth your while to rent a navigation system, especially if you have a smartphone with GPS or own a portable system you can bring with you.

HD radio. Unless you’re really, really hooked on HD radio, which offers great sound but spotty coverage, we’d skip it.

You’re often given three fuel choices: agree to return the car with a full tank; prepay for a full tank; or let the rental company top up the tank when you return the car.

The first choice is best if you start with a full tank. Fill the car immediately before returning it—and save that receipt!

Buying a tankful up front makes sense if you can contrive to return the car almost empty. If you return it partly full, you don’t get a refund. In other words, you get to pay not just for your own fuel but some of the next customers’, too.

Letting them fill it for you could be the worst bet. Rental companies can add “service” charges that could tack on several dollars a gallon.

Electronic toll trolls

Many regions are adopting cashless electronic highway tolls—EZ-Pass in the northeast, SunPass in Florida, FasTrak in California, and so forth. Typically you’ll pay $3 to $5 a day for the car’s built-in e-toll transponder, whether you go through any tolls or not, plus the tolls themselves.

Sometimes you’re given a choice of having the transponder activated or not. If you decide mid-trip that you’ll need it after all, you’ll be charged for all the days you didn’t have it, as well as those you did. If you turn down that privilege and happen to breeze through a cashless toll, be prepared to pay a big charge, $100 or more, plus the toll, and perhaps other fees.

This table shows typical sedans you’ll find in retail rental fleets, according to their websites. Note that most sites mention a model name with the caveat “or similar.” That means you often can’t know for sure that you’ll get the exact car you wanted. Try calling the rental location to nail them down on what they have on hand.

Large chains like Avis, Enterprise, and Hertz also rent luxury cars, usually BMWs and Mercedes-Benzes, in select markets and locations.

Models that we consider especially mediocre, based on our testing, are marked in Italics. There is no reason to ruin your vacation by renting a model that has an uncomfortable seat, harsh ride, and/or poor fuel economy. Those include the Chevrolet Impala, because for now most rental Impalas are the previous-generation Impala Limited, which GM continued making for rental fleets, instead of the much nicer Impala redesign that bowed in 2014.

Zipcar is a leader in the “car sharing” movement, a low-hassle approach to very short-term car rental—from an hour or two to a week. Typical rental charges run about $8 to $9 an hour, which includes gas, insurance, and 180 miles. The varied fleet mostly has small and midsized sedans, but it includes vans, pickups, and luxury cars at select locations.

Despite being acquired by Avis in 2013, Zipcar maintains its youthful, socially conscious vibe. You first buy a membership, for $6 per month or $60 per year, and they mail you a personal key card that will enable you to access cars you then book by phone or online. Members can be as young as 18 for some college students.

Members are expected to leave plenty of fuel for the next renter, and fill up (at Zipcar’s expense) if necessary. They’re also enjoined to leave the car free of travel trash, return the car to the place where they picked it up, and not be late.

The honor-system approach doesn’t always work out. Numerous complaints cite cars that have been left with little gas and someone else’s food waste. Pickings may be slim in some places, too. But for people who need a car only occasionally, Zipcar can be a convenient and low-cost alternative to car ownership.

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