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I’ve been a loyal Costco member for 18 years. And for roughly the past five years or so, I’ve been shopping at Costco weekly to stock my pantry and fridge with groceries and household essentials. I’ve spent my fair share of time at Costco.

And because of this, I know which savings strategies are worth employing and which mistakes are likely to result in wasted money. But if you’re a new member, you may not know the ins and outs of maximizing your Costco savings just yet. And that means you risk falling victim to some of the blunders I made back in the day.

Here are three to avoid.

1. Not upgrading to the Executive membership

I was a Costco member for several years before an employee suggested I get the Executive membership. At first, I was hesitant, since it costs twice as much as a basic Gold Star membership. But then I realized what a great deal it is.

With an Executive membership, you earn 2% cash back on your Costco purchases. And that’s on top of any cash back your credit card gives you.

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Of course, the trick is to spend enough money at Costco to make back the cost of an Executive membership upgrade and come out ahead financially. Based on the store’s current fee structure, you need to spend $3,250 a year at Costco to break even on the upgrade. That’s because a Gold Star membership costs $65 per year, but an Executive membership costs $130 per year, or $65 more.

But if you don’t make back your Executive membership upgrade fee, Costco will let you downgrade to a Gold Star membership after a year and refund you the price difference. So I say you might as well go for the upgrade and see what happens.

Say you only spend $1,200 at Costco after a year, and therefore only get $24 back from your Executive membership. If you switch to a Gold Star membership at that point, Costco will give you back the $41 you didn’t earn. Really.

I wish I would’ve started with an Executive membership, because while I wasn’t buying as much food in bulk back in the day due to not yet having kids, I also made one-time purchases at Costco, like clothing and electronics, that probably would’ve made the higher-cost membership worth it. And I’m certainly glad I switched over when I did. Since upgrading my membership, it’s been worth it every year.

2. Not shopping when their gas tanks are near empty

When I first started shopping at Costco, the idea of buying gas there wasn’t even on my radar. I was so used to filling up on certain days of the week at my local gas station that the thought didn’t cross my mind.

That was a mistake, though. I later realized that Costco has some of the best gas prices in town. And not only that, but one lesser-known benefit of Costco fuel is that it’s TOP TIER certified, which means it’s actually designed to lead to better engine performance.

Now, when I plan my Costco outings, I make sure to do so when my car’s gas tank is pretty low. That way, I can fill up while I’m there and take advantage of those lower prices and higher-quality fuel.

3. Not giving Kirkland products a chance

I’ve never been the type to care about name brands in the context of clothing or footwear. But I’ll admit that when it comes to food, I can sometimes be a bit picky about the products I bring home.

That pickiness cost me a lot of money as a new Costco member, though. Back when I first started going to the store regularly, I almost always passed over the Kirkland products because I assumed they were inferior versions of the brands I knew and loved. I then did some research and realized that not only is Kirkland, Costco’s signature brand, high in quality, but it’s considerably cheaper than name brands.

Costco has explicitly said that its goal is to offer its Kirkland line for at least 20% less than name brand counterparts. So buying laundry detergent with the Kirkland label, for example, could mean spending $16 or less on a product that might otherwise cost you $20. That’s not a deal you want to pass up.

And if you’re worried you won’t like your Kirkland products as much as your name-brand buys, remember that Costco guarantees your satisfaction on every purchase you make. So if a Kirkland product doesn’t work out, just bring it back for a refund.

When you’re new to any given experience, it’s common to make some missteps. But don’t fall victim to these blunders like I did. Take my advice and consider an Executive membership from the start, fill up your gas tank at Costco as often as you can, and load up on Kirkland products for the added savings.

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The Ascent does not cover all offers on the market. Editorial content from The Ascent is separate from The Motley Fool editorial content and is created by a different analyst team.Maurie Backman has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Costco Wholesale. The Motley Fool has a disclosure policy.