From Hercules to Bigfoot, the world loves a myth, and autodom has its fair share. We’ve even rounded up some of the dumbest car myths readers have heard. Spoiler alert: the break-in period of a car engine is not on that list. That’s good, because it’s not a myth at all.
A break-in period – not to be confused with where your car is most likely to be stolen – refers to the time it takes for an engine’s internal organs to become comfortable working together. Like leather boots that mold to your feet, piston rings and cylinder walls rub against each other as the engine runs. This friction causes wear, which creates dirt that ends up in the oil over the life of the car. That’s why enthusiasts and technicians may send samples to an oil analysis laboratory to help monitor engine health and ensure wear is within accepted tolerances.
The myth at play here is whether modern car engines are run-in at the factory so this initial bit of wear and tear isn’t a problem when you get your shiny toy from the dealer for the first time. The truth is that engines can be tested for defects, but it is not the same thing. And some manufacturers still have guidelines for safely breaking in your new car.
The tribology lesson has started
Merriam-Webster defines tribology as “a study concerned with the design, friction, wear, and lubrication of interacting surfaces in relative motion (as in bearings or gears).” Lake Speed, Jr. is the son of NASCAR veteran Lake Speed, and a true tribologist. To save us the hard work, he made a great YouTube video with a comparative oil change trend analysis, using science to see if the engine is indeed breaking in.
Speed also discusses why he changes the oil early, and two reasons (lease cars and fuel economy standards) why manufacturers have extended their oil change interval recommendations.
What about hybrids and electric cars? Hybrids have internal combustion engines and may have their own specifications for engine break-in. As for EVs, new parts like brakes and tires can take some time to break in. Tires will undergo heat cycling and release new tread in the first 500 to 600 miles that may contain factory lubricant residue. Likewise, it can take about 500 miles for the brake pads to settle into their friction surfaces.
What do car manufacturers say?
Perhaps the biggest factor contributing to the no-engine-break-in myth is the variation in how – and whether – automakers define and specify break-in recommendations.
BMWsays, for example, “Engine break-in used to be a standard procedure on new cars. And it’s still the case that you should avoid running the engine at high RPM for the first 1,300 miles.”
Ford also states unequivocally in the 2025 Mustang owner’s manual: “Your vehicle requires a break-in period. Drive your new vehicle a minimum of 100 miles (160 km) before performing extensive throttle maneuvers and a minimum of 1,000 miles (1,600 km) before operating your vehicle at high speeds or in high track conditions.”
Subaru indicates a break-in period for the 2025 Outback. A search of the 2025 Mazda CX-30 manual revealed no mention of a break-in period, but precautions were suggested in 2021. Picked up a new Chevrolet C8 Corvette? There is a video about the break-in procedure of the 2025 Corvette Chevrolet’s YouTube channel – and the tachometer changes after the car has been run in.
Unless you drive a Bugatti, which requires the engine to be broken in during a 250-mile drive before delivery, it’s best to ask your dealer and consult the owner’s manual before re-striping the lot.
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