You may have seen the August 17 article from The New York Times on decision fatigue (it’s been one of the ten most emailed articles on the Times’ website since it went live). Decision fatigue, the Times writes, “helps explain why ordinarily sensible people get angry at colleagues and families, splurge on clothes, buy junk food at the supermarket and can’t resist the dealer’s offer to rustproof their new car. No matter how rational and high-minded you try to be, you can’t make decision after decision without paying a biological price.” Every time we make a decision, we’re using mental energy. And like any muscle, that part of our brains can tire out with frequent use. The Times explains that decision fatigue is “different from ordinary physical fatigue — you’re not consciously aware of being tired — but you’re low on mental energy.”

Once we get low on mental energy, our brains start taking shortcuts, making impulsive decisions without thinking through the consequences, or doing nothing, ignoring the choice altogether. While impulsive decisions seem to be the riskier of the two shortcuts (think of a stressed-out college student plagiarizing a paper during finals week), doing nothing has its pitfalls as well (that same college student doesn’t write the paper at all).

So, why is an automotive writer covering an article on the impact of fatigue on decision making? Because car buyers are at risk for it, and it can end up costing you thousands.

Think through all the decisions you have to make when buying a car: are you going to shop new or used? Do you want a car or an SUV?  Which model do you want? Which trim should you get? What option packages should you choose? Are you going to use financing, pay cash, or lease? Should you use bank or dealer financing? Should you take the cash-back or low-interest financing offer? Is the dealer offering a fair price?  Should you take it? Which color car are you going to choose?  Do you want the extended warranty? Should you get undercarriage protection and have the dealer scotchgard the interior? Do you want the service plan? What about tire insurance?

These questions only scratch the surface of the hundreds of decisions car buyers face. It’s a perfect setup for decision fatigue and it’s something that some unscrupulous car dealers count on.  You’re tired, so you stop reading the fine print or agree to extras, and money flows out of your pocket into theirs.

As risky as decision fatigue is to the car buyer’s bottom line, you can avoid it. Break each part of the buying process into individual steps. Do your research online to narrow your choices down to the three cars you want to test drive.  Test each of them on separate days, take notes on each one and give yourself time to absorb each of them. If the dealer you test drive with wants to talk price, politely and firmly let them know you’ll be in touch. Once you’ve decided which car is for you, check out the features. Go back to the dealer if you want to see how each feature works or looks, and build the exact car you want online, so you can take your time and decide if each option is worth its price.

Once you know the car you want and how you want to outfit it, negotiate the price online.  You can use the U.S. News Best Price Program to find a pre-negotiated price from a certified dealer, or you can get quotes from multiple dealers. Negotiating over email takes the pressure off and gives you time to make the right choice. Once you have a price in hand, go to your bank and credit union and see what kind of financing they offer, and see if the dealer can match or beat it. Do as much of the work online, on your own time, so that when you get to the dealership the only decision you’ll have to make is if you’re going to sign the paperwork in blue or black ink. You’ll be rested, ready to read the fine print and say no to any extras that could impact your budget. Best of all, you’ll be less likely to wake up the next day with a severe case of buyer’s remorse.