Mechanics Name 10 Things They’d Never Do With Their Own Cars — And Why modern car tech makes it more important

Automotive technicians who spend their days diagnosing and repairing vehicles say there are 10 common practices they would never tolerate in their own cars — mistakes that can worsen as vehicles become more software-driven and dependent on sensors. The list, compiled from interviews with master technicians and shop owners, stresses routine maintenance, correct fluids and parts, and honest communication with mechanics.

Leading the list is a simple but persistent warning: do not neglect scheduled maintenance. Bogi Lateiner, a Phoenix-based master automotive technician and owner of Girl Gang Garage, said oil changes are the closest automotive equivalent to basic hygiene. "Can you get away with only brushing your teeth once a month? You'll survive, but you're going to lose your teeth," she said. Lateiner advised changing oil far more frequently than some manufacturer intervals, recommending many owners cut published oil-change intervals roughly in half and not exceed about 8,000 miles on full synthetic oil for certain European cars.

Technicians also cautioned against relying solely on in-car maintenance reminders. Robin Reneau, owner and lead technician of Georgia Auto Solutions, said onboard reminders are based on generic algorithms and mileage assumptions that may not reflect an individual vehicle's operating conditions. Short trips, towing, extreme temperatures and progressive engine wear can accelerate oil degradation even when a dashboard indicator hasn’t illuminated, she said. Reneau recommends drivers check oil level and condition manually and track consumption rather than treating the vehicle’s reminder as definitive.

Another recurring theme is parts and fluids compatibility with vehicle software and calibration. Grace Claudio, a New York-based master automotive technician with BMW Manhattan, urged owners to use original equipment manufacturer (OEM) parts rather than cheaper aftermarket alternatives. In some modern cars, she said, the vehicle’s systems may not "register" an aftermarket battery or part, which can leave code warnings active or cause ancillary systems to behave incorrectly. Lateiner made a similar point about fluids: using the manufacturer-specified oil, coolant and fuel octane rating matters because engine control units and emissions systems are calibrated for specific chemical and thermal properties.

Technicians warned against short-term fixes that can complicate future repairs. Lateiner described over-the-counter "stop-leak" products for oil, coolant, power steering fluid and tires as temporary bandages that often create more damage than they solve. She said tire sealants can gum up wheel components and make professional tire service more difficult, and that internal engine or cooling-system additives can clog sensitive passages or sensors.

Bodywork and interior fitment also carry hidden risks. Cheyenne Ruether, a Las Vegas-based master auto body technician, advised caution with vehicle wraps in sunny climates, noting that prolonged ultraviolet exposure can cause cracking or delamination and make removal difficult. Claudio highlighted a safety hazard with improperly sized floor mats: an ill-fitting rubber mat layered over a carpet mat can trap the accelerator or interfere with the brake, increasing the risk of an unintended acceleration or reduced braking performance.

Tires themselves were another focus. Technicians advised against fitting used tires as a cost saving. Claudio said sellers sometimes provide tires that do not match the vehicle's specified size or that have hidden defects, such as sidewall bubbles. Industry guidance calls for careful attention to tire age as well as tread: manufacturers like Michelin recommend replacing tires no later than 10 years after manufacture, and many automakers advise replacement around six years regardless of apparent condition. Vehicle owners can determine a tire’s manufacture date from the four-digit portion of the Tire Identification Number on the sidewall.

Modern vehicles increasingly rely on onboard diagnostics and warning systems, making it risky to ignore dashboard alerts. "Our cars today especially are designed to self-correct a lot of things," Lateiner said. When a vehicle can no longer compensate for a fault, it illuminates a warning light and stores diagnostic trouble codes that guide technicians to the underlying problem. She advised consulting the owner’s manual to interpret lights and, if unable to afford an immediate repair, asking a shop whether the vehicle is safe to drive and how long it might be operated before causing further damage.

Finally, technicians emphasized the value of honest, detailed information when a car is brought in for service. Lateiner said misleading or incomplete descriptions of a problem force technicians into less efficient diagnostic paths. She suggested recording audio or video of intermittent noises or bringing a passenger on a test drive to help pinpoint conditions under which a fault appears.

Mechanics framed these cautions against a backdrop of increasing vehicle complexity. As more functions shift from mechanical systems to software-controlled modules and sensor networks, seemingly small choices — using the wrong fluid, installing an incompatible component, or dismissing a warning light — can interact with embedded electronics and diagnostic logic in ways that increase repair costs or create safety risks. The technicians’ advice underscores that preventive maintenance and adherence to manufacturer specifications remain important even as cars become more like computers on wheels.

Proper maintenance can require an upfront expense and a bit of attention, but the mechanics interviewed said that approach typically reduces long-term repair costs and safety risks. For owners unsure how to act, the technicians recommended consulting the owner’s manual, performing basic checks such as oil-level inspections, and asking reputable shops for clear guidance on what is safe to delay and what requires immediate attention.