Definition
To 'run in' a new vehicle, you operate it cautiously at low speeds initially, to ensure the longevity and integrity of the engine.
磨合（新车）
With our new car, we decided to drive slowly for the first few hundred kilometers to run the engine in.
我们的新车刚买时，决定在前几百公里缓慢行驶，让引擎磨合。
To ensure optimal performance, the factory conducts a thorough run-in of the machinery before it leaves the production line.
为了确保最佳性能，工厂在机器离开生产线前会进行彻底的磨合。
Following the dealer's advice, he carefully ran in his new electric car.
遵循经销商的建议，他小心翼翼地磨合了他的新电动车。