No matter where you’re traveling, renting a car is one of the best ways to actually experience your destination. With your own car, you can get off the beaten path, stop whenever something catches your eye and enjoy sights the average tourist never lays their eyes on.

But, that doesn’t mean renting a car is cheap. Depending on where and when you go, car rentals can be absolutely expensive.

If there’s one travel fail that can make it even worse, it’s not shopping around for your rental. Here’s why:

IF YOU’RE one of those people who book a rental car and never thinks about it again, you’re probably overpaying.

That’s because, like airfare, the price of any given rental car in any given destination can rise and fall by the day — or even by the hour. I’ve rented cars that have dropped down to a third of the price within a few weeks of my trip, just like I have rented cars that have ballooned in price after I already locked in a super-low price.

Keep in mind that the price of a rental can vary depending on where you book. Websites that offer rental cars are just as likely to be competitive as they are to be all over the place.

Case in point: Let’s consider a random rental situation in November out of Zurich.

If I search for a rental car out of ZRH for Nov. 7-14, here are the cheapest prices I see on several websites:

Expedia: $963 total for the week for a Ford Fiesta or similar

Chase Ultimate Rewards: $315.57 for the week for a Volkswagon Golf or similar

Kayak.com: $206.80 for the week through Flizzr for an Opel Adam or similar

You get the point, and that was a single random inquiry. If we played around with dates and destinations, we could find rate disparities that would blow your mind. It’s important to know this because the best way to save on car rentals is to avoid booking your rental and forgetting all about it.

Believe it or not, there’s an easier way that can save you hundreds of dollars, and it’s not all that time-consuming, either.

THE BEST way to save on rental cars is to shop around, book the best refundable fare you can find, then check in every few weeks. I have done this for rental cars in Europe, the Caribbean and the U.S., saving thousands as a result.

The key to making this work is booking refundable fares that can be canceled up until the day before your trip. With a refundable booking, you can cancel any time you get a better deal.

There’s also another, lazier way to do it.

You can book your auto rental through AutoSlash.com or connect a previously booked rental to the website. Either way, you’ll get email updates whenever prices drop for your rental with a variety of carriers.

If you book with AutoSlash.com, you can even set it up so your car rental is canceled and rebooked for you. It doesn’t get any easier than that.