Should you break in your car? Surely it comes from the factory ready to go, but that's not true for all cars. Yes, some performance automakers will put the vehicle through its paces, like the Acura NSX, before it lands on dealership lots. That's because it's a performance car, and Acura wants consumers to be able to bring their car to the track the moment they get the keys. However, most mass retail vehicles require a little time to break in.
A lot of it has to do with warming up new components. For instance, brake pads and rotors have yet to get much use before you get behind the wheel. They need to mate properly. And while you might have noticed colored lines on new tires, they will wear off, but new tires and brakes have film left over from manufacturing that can affect your stopping power. These are just some of the components that require a little break in to keep your car running well.
Avoiding too much strain on the engine is good advice to go by. The golden rule is to keep your vehicle from hitting 4,000 rpm or hitting the redline for the first 500 to 1,000 miles. This is great advice for cars with manual transmission, too, as the clutch may need some time to get in the rhythm of things, and shifting between the lower gears can help it run smoothly early on. Put too much pressure on the engine when breaking it in, and you can expect worn down cylinder walls and camshaft lobes that don't work correctly.
During the first 500 to 1,000 miles, the piston rings need to mate up with the walls of the cylinder. According to some sources, there can be imperfections in the cylinders from manufacturing that the rings can wear down and smooth out when they expand once they reach the optimal operating temperature. Otherwise, you can see increased oil consumption, poor performance, or both. This is also one of the reasons you should avoid short trips early on.
Sure, driving around the city can be useful, because driving with varying engine loads and different gears can also help break in the engine. However, driving on the highway for a bit can also give your car more time to warm up. Just avoid using cruise control, or you'll be underlining the whole benefit of changing RPMs on long drives. Driving on the highway will also help keep you from idling too long. Lastly, since we've been asked, when it comes to towing, you shouldn't tow anything early on. This ties back to the film on the brakes, and you need all the stopping power you can get when towing.