Many of you have a card in your wallet that could potentially save you hundreds of dollars, and you’re not even aware of it. We’re talking about your Costco card; the one you use to buy 36-pack rolls of toilet paper and boxes of breakfast cereal large enough to feed your high school graduating class.

You already know it saves you a bundle when buying in bulk, of course. That’s why you joined Costco in the first place. But do you realize that it can also save you heaps of money on your next car rental?

The humble Costco membership can be a gold mine of car rental deals. Here at AutoSlash, we spend a heck of a lot of time analyzing car rental pricing. After looking at thousands of reservations, we can tell you with a great deal of certainty that if you’re not a Costco member, you’re missing out on a wealth of great car rental discount codes that’ll many times beat almost every other rate out there.

For example. AutoSlash users living in New York already know that renting a car in the city on a summer weekend can cost more than a nice piece of property in Cleveland. (Those of you outside the Big Apple, just take our word for it and count yourselves lucky.)

Using a major car rental company you’d know the name of if we told you, we recently priced out a weekend rental in Manhattan from Friday to Monday. The price for an economy vehicle? A whopping $413.97. Chauffeur not included.

After getting over the initial sticker shock and picking our jaw up off the floor, we surfed on over to Costco's website, clicked on Travel in the main menu, and then clicked on rental cars. This is the place where you find all the various coupons and discount codes that are available to Costco members.

So, say we take that same weekend rental that was going to cost us $413.97, and we apply the correct discount code from Costco's website. What do we find? We find that the rate magically drops to $313.29. Holy cannoli, a $100+ savings just for putting in a little discount code? Believe it.

We don’t pretend to be math geniuses over here at AutoSlash, but say you got the personal membership ( – a $50 annual fee – and never even went to Costco, instead just renting cars from time to time. On your first time out, saving $100 on a weekend rental, you’ve not only got your $50 back, you just made $50. We’ve played supposedly loose slot machines that are less generous.

Of course, not all discount codes – not even Costco ones, it must be said -- are created equal, so it makes sense to comparison shop with these codes before you book. Some codes work better for some rentals than others. We’ve also seen good discount codes for BJ’s Wholesale, AAA and American Express cardholders. You might find that membership truly does have its privileges.

Note: Rental companies can and do ask for proof of membership when using these sorts of discounts, so be sure that you are eligible before making a reservation with one. Otherwise you could be in for a whopper of a bill when you get charged the walk-up rate because your discount was denied.

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