Often, rental agencies will be overstocked on larger, nicer vehicles—say, SUVs and luxury cars. But they don't want to advertise that on their websites and price them for less than your basic compact car. A few years ago, a Thrifty franchisee in Nashville came up with an idea: Why not create a car class where people, well, don't reserve a specific car class?

To sweeten the deal for the customer, they priced it right near the bottom of the rate structure—between the price of a compact and a midsize—and even guaranteed that it would always be at least a midsize car. But it could be a premium or luxury car, SUV, or even a convertible—great for those sunny Hawaiian days!

The idea took off spread to Thrifty locations across the country and even to Thrifty's sister brand, Dollar, where it got the slightly more cumbersome name of "Lock Low 'n' Go."

If you're thinking about booking a compact or midsize car with Thrifty, why not book a Wild Card? For about the same price, you'll have the chance at getting something nicer and fancier without paying an extra cent.

Of course, you can't be picky about the kind of car you want to drive, since the car you'll get is determined by the renting location and could be anything—even a minivan. And be aware that convertibles can have tight back seats and small trunks, so if you've got four adults, you might want to stay away from the Wild Card if you're renting from a location that stocks ragtops.

If you're feeling a ride on the wild side though, Thrifty's Wild Card (and Dollar's Lock Low 'n' Go) can net you savings on something you might not normally pay for.

Note that at AutoSlash, the Wild Card option will sometimes show up as a standard size car on the pricing grid. When you click through to the car selection screen, you'll see a description of "Standard Special" and a description of "Midsize car or larger".

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