A Chicago mechanic thought he was dealing with a straightforward oil pressure sensor issue. After replacing the part twice and still seeing the warning light come back on, he discovered the real problem—and it pointed to some shady dealing by whoever sold the car. Mechanic Discovers Shady Business With Nissan In a trending video with more than 5,600 views, mechanic Jeremiah (@jrsgaragebtym) explains that a customer brought in a Nissan they'd purchased about a week earlier. The oil pressure light had come on shortly after the purchase, so the customer replaced the oil pressure sensor before bringing it to Jeremiah's shop. When the new sensor didn't fix the problem, Jeremiah replaced both the oil pressure sensor and the oil pressure switch. The light stayed off for a while, but eventually came back on. At that point, he says the customer feared the worst-case scenario: a failed oil pump. The actual problem turned out to be even more disturbing. "Well, it happened to be that they bought a [expletive] car with plastic and metal material, not like dust, but actual [expletive] material clogging the pickup tube," he says in the video. OWNERSHIP STORIES Viral stories from across the web Our team of experts tracks what owners are saying about car-shopping, repairs, the daily driving experience and more on social media. And the large debris wasn't the only red flag. Jeremiah says whoever sold the car had filled it with extremely thick oil—thicker than anything he'd encountered in his career as a mechanic. "And whoever sold them the car sold them the car with the thickest [expletive] oil I've ever seen," he says in the TikTok, implying the thickness as meant to mask the engine's problems long enough to get the car off the lot. In the video's caption, Jeremiah describes the situation as a "typical salesman screws customer kinda deal." Gallery: 2026 Nissan Rogue Dark Armor Common Tactics Dealers Use to Hide Engine Problems Used car dealerships have a playbook of tricks to hide mechanical issues long enough to get vehicles off the lot. According to Vista Motors, one of the biggest red flags is the engine oil. Clean oil should be light brown or amber and smooth. Dark black or gritty oil shows old oil or engine wear, while milky oil can indicate water in the engine. German Precision outlines common tactics dealers use to conceal problems: Hiding mechanical problems: Dealers may sell cars with significant engine, transmission, or suspension issues that aren't visible during a quick test drive. Problems like clogged oil pickup tubes or failing parts often don't show up until after the sale. Odometer rollback: Rolling back mileage to make a car appear less used than it actually is. Signs of excessive wear on pedals, steering wheels, or seats can indicate the odometer doesn't match the car's true usage. Strong scents to mask damage: Overpowering air fresheners can hide signs of mold, water damage, or mechanical issues. A car that smells too strongly of fragrance might be covering up deeper problems. Rushed sales tactics: Pressuring buyers to "act now" or skip independent inspections prevents customers from discovering issues before purchase. Legitimate dealers welcome outside mechanics checking their vehicles. Poor or missing maintenance records: When dealers can't provide service history, it's often because the car wasn't properly maintained, leading to problems like debris in the engine or worn-out components. The best defense against these tactics is getting a pre-purchase inspection from an independent mechanic before buying any used vehicle. A professional can spot warning signs like hidden damage or deferred maintenance that dealers hope you won't notice. Commenters React "This is why you take it to a mechanic before you buy it," a person said. "Wow what people will do to sell the vehicle," another wrote. "I’m glad you’re not like other shops and actually find the issue! Kudos to you," a commenter added. Motor1 reached out to Jeremiah for comment via TikTok direct message and comment. This story will be updated should he respond. We want your opinion! What would you like to see on Motor1.com? Take our 3 minute survey. - The Motor1.com Team