When an Instagram user asked for new car dealership negotiation tricks, commenters weighed in with the usual.

These included: Buy at the end of the month, hoping the salesperson has a quota to make. Get offers from multiple dealerships and let them bid on your business. Or say you have a trade-in and want dealership financing when asking for the final price—even if you “change your mind” and pay cash without a trade-in. But one commenter came in with a tactic no one was ready for.

Molly said she’d been going to school in Boston when her professor needed a new car. He taught Conflict & Negotiation, so he decided to enlist his students’ help in calling the dealership. He “had one entire 50+ section of his class get him quotes on a specific Camry in the Boston area as an assignment.”

The Camry in question was at a Toyota dealership near Fenway. The negotiation professor took the lowest quote and went to visit the dealership in person. He said, “’I want this car for this price’” and put down his AMEX.”

The car dealership negotiations begin

Crowdsourcing your car quotes and going with the lowest one is pretty smart. But apparently, the professor’s negotiations had just begun. You see, the dealership didn’t want to let the car go for such a low price without getting some interest payments. The salesman said, “No that’s the financing price.”

This negotiation professor likely understood beforehand that he’d have to get dealership financing if he wanted the lowest possible price. But he knew he’d have some leverage if he “gave up” on paying by card. He said, “I want the points, what can you do for me?”

Molly explained that the salesman was still eager for the sale. “They tried lifetime oil changes, nah. Add ons like window tinting, pass.”

Then the professor appeared to pull an idea out of thin air. “He saw a guy outside washing their cars and said ‘Can you give me free lifetime car washes here? Any time I want them, I bring it in, drop it off, and someone like him washes my car and I can pick it back up?’”

The salesman jumped at the suggestion, saying “yes” immediately.

The professor then “financed the car, paid it off with the Amex a week later.” That alone is a smooth move. Though, you’d want to make sure beforehand that Toyota will let you pay off their loan in one go, with a card. But that was far from this professor’s endgame.

A daily car wash, all for parking

The first weekday the negotiation professor had the car, he dropped it off at the dealership for a wash. After work, he picked it up. Then the next day, he did the exact same thing. The salesman must have wondered what kind of neat freak he was dealing with. By the end of the first week, he might have begun to suspect something else was going on. But by then, it was too late.

According to Molly, her professor “dropped his car off every day on his way to work for the life of the car ‘to get washed.’ It wasn’t about the car wash: it was FREE PARKING RIGHT IN THE HEART OF BOSTON FOR LIFE.”

Wowza, that’s a checkmate right there. The professor may have never cared about the make and model, or even his final price. Though a Toyota Camry is a budget bargain likely to last as long as any other sedan on the road. He had an ulterior motive and played the salesman perfectly. But hey, that’s what he does for a living.

Molly concluded, “This is literally why he’s one of the most brilliant negotiation minds in the world. Totally not kidding, he literally worked on international peace agreements.”