My 2018 Hyundai manual says the motor is broke in either at 600 miles.break in oils usually contain high amounts of zinc/phosphorous which is harmful to modern car emission systems. Just follow the manufacturer’s process for break-in. Varying speeds don’t accelerate and brake aggressively I wouldn’t sweat it. Modern synthetics do an exceptional job in what they were intended for.
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VEHICLE BREAK-IN PROCESS
By following a few simple precautions for the first 600 miles (1,000 km) you may add to the performance, economy and life of your vehicle.
- Do not race the engine.
- While driving, keep your engine speed (rpm, or revolutions per minute) between 2,000 rpm and 4,000 rpm.
- Do not maintain a single speed for long periods of time, either fast or slow. Varying engine speed is needed to properly break-in the engine.
- Avoid hard stops, except in emergencies, to allow the brakes to seat properly.