How to Break in a New Car There are plenty of ways to break in your new car. Some of them are the right way. It's a thing of beauty: A brand-new car,shiny and crisp. It makes you want to spend the whole evening walking around it.If you're installing a new engine,simply give it a few seconds of wide-open throttle in a high gear. For the first thousand miles,avoid constant speeds and throttle settings. If you commute in normal stop-and-go traffic,you'll be fine. I advise against cruise-controlled sojourns across Nebraska. Bearings The admonition to keep engine revs low for an extended break-in period stems from the days when bearing and crankshaft manufacturing tolerances were far less rigorous and lubricating oil wasn't nearly as good. While modern engines are assembled to much the same design clearances,the tolerances are much tighter,meaning the variability is smaller,greatly reducing the possibility of a tight spot ... Read more »