This website never fails to save me (lots of) money on car rentals—and it’s free!

With rates for car rentals fluctuating every day, it’s not easy to know if you got the cheapest price. Here’s the solution: Input your car reservation details into AutoSlash.com. Savings on my last three rentals of a week or less: $240, $190, and $87.

How does it work? The site tracks the rates for your dates and scouts competitor pricing, including coupons and discount codes. If a lower price for the same rental becomes available, you’re notified by e-mail and can rebook your reservation.

To be clear, you’re not required to book one of AutoSlash’s suggestions from their quote. You can book any car rental you desire as long as it has a free cancellation policy—without that, you’re locked into the rate you originally booked.

AutoSlash can find lower rates for domestic and international car rentals.

You can also make a new reservation through AutoSlash. Fill in all the details in the “Get a Quote for your car rental” box on the homepage (origin, destination if different than origin, dates, etc.). AutoSlash will send you a selection of the cheapest rates (with free cancellation) to your email.

The site is easy to navigate. Just fill in the requested info.

You’ll receive an email confirming your rental is being tracked.

Then sit back and wait for the emails with lower rates to arrive.

The savings are significant. Here’s one example: I input the details of a car rental that I had booked on Hertz for $331. Within a day, AutoSlash had found rates as low as $90 (with Budget; the Hertz rate they found was $112).

On another occasion, AutoSlash emailed me several weeks before my trip that they’d beat my Hertz rate of $332 with a rate of $123 (in this case, also with Hertz).

It’s easy to make the new booking. Click on the link and accept the new reservation. Then cancel your original reservation. (When I went to the Hertz site to do this, I saw my new reservation was already listed.) That’s all there is to it.

Note: Be sure to have Autoslash track your new booking, too. On several rentals, I’ve received three price cuts!

The first few times I used AutoSlash, I searched a few of the major aggregator travel sites to see if I could find a better rate with free cancellation. No luck. Since I started using AutoSlash, I’ve saved money on every rental reservation.

Twist’s Take: Have AutoSlash track your car rentals. It’s free, involves little extra effort, and will save you real money.