Engine Break-In: What You Need to Know

BMW S65 Engine Block 6 photos
Photo: BMW
engine-break-in-what-you-need-to-knowFord BroncoEngine openedPistonBMW M4
Some people support the old-school of break-in engines and those who are saying that there's no need for that anymore since this process is already made at the factory. But you might want to know how to do that if you're planning to keep your brand-new car for years to come.
In theory, there is no need for a break-in process, but as long as the carmakers call you back for a quick oil change in less than 10,000 or 15,000 miles, they know something. They know that their new engines should be treated carefully.

In addition, if you follow the break-in procedure, you won't harm your car's engine. But if you have to do that, and you are not doing it, you can really damage it. Sure, it will last as long as the warranty lasts. But who knows what will happen after that expires? If you are leasing the car, you might not care at all. You'll drive it according to the manual since you'll give it back anyway.

Carmakers quietly admit it

Take, for example, Ford Bronco. The owner's manual states that "The oil consumption of new engines reaches its normal level after approximately 3000 mi (5,000 km)." That's a clear sign that the engine is not quite broken-in from the factory. Of course, it's just an example, but if you carefully read your car's manual, whatever the brand, you'll find similar clues telling you that you have to break in the engine. And don't think Europeans are better at this, because they're not.

For instance, the BMW M4's manual stipulates in its owner's manual that for the first 2,000 km or 1,200 miles, the maximum engine speed should not exceed 5,500 RPM. Moreover, the top speed is limited to 170 kph (105 mph). Furthermore, wide-open throttle and "pedal to the metal" should be avoided until the mileage mentioned above is shown on the car's odometer.

Photo: BMW
Moreover, the recommendations claim that even after that, between 2,000 and 5,000 km (1,200 to 3,100 miles). But still, you should ensure you don't travel at speeds over 220 kph (137 mph) for too long. Unfortunately, no exact figures are offered, so it's up to you what "too long" stands for.

As some manufacturers still recommend breaking in your engine, we decided to tell you how it's done. But first, let's ensure everyone understands what breaking in means.

This represents how various components get used to each other for the initial hours of their functioning together. Things like the engine's piston rings and the cylinder walls have to work together for a while before they can reach optimum performance levels. The nay-sayers argue that there's so much precision in today's industry that this is no longer needed.

In the past, tiny bits of metal used to be brushed off or turned off by the initial cycles of the engine because the drilling machines weren't precise enough, leaving bigger tolerances than today. However, even now, things are not perfect and will never be. Furthermore, seals must work at a specific temperature to do their job correctly. So, at first, they need to be warmed up a little. Still, the amount of time and the working hours it takes to do so varies a lot. As I said, the debate continues to this day.

Photo: Michaela Pereckas/Flickr
Modern engines will take up to 1,000 miles (1,600 km) on average to settle in. In the past, that figure was about 3,000 miles (4,808 km), but it's no longer the case. During this time, you could use some basic rules if you just want to keep your peace of mind.

Don't floor it!

Keep the revs decent. Now, depending on whether you're breaking in a diesel or a petrol engine, you'll need to keep some RPM figures in mind. Usually, diesel engines rev less than gasoline ones, which means that if we're recommending you don't go over 3,500 RPM on a petrol engine, you should bear in mind that for a diesel, that number is lower, maybe around the 2,500 mark. Again, it depends on the engine itself. As a rule of thumb, keep it below the halfway point of zero and the redline.

At the same time, you don't need to baby the throttle; just be careful not to go over the aforementioned limit too often. While accelerating, do it confidently, applying wide-open throttle from low RPMs, but avoiding kick-downs. Just don't do that on a cold engine!

One of the aims of breaking in an engine is to make sure that the piston rings seal against the cylinder bores. That is done using gases emitted during running that force the rings outwards. That's why it is good to provide high pressure initially.

Old oil out, new oil in

An old saying says, "Oil is the life of an engine." It does the internal cooling, cleans debris, and takes out small pieces of metal resulting from the break-in process. Therefore, refresh it after the first 100 miles (160 km) if possible. Anyway, carmakers recommend the first oil change to be performed after 1000 miles (1,608 km).

Ford Bronco
Photo: Ford
In an ideal world, you should replace the oil and oil filter after the first 100 miles and then again after 1000 miles. If you can, inspect the oil filter cartridge after it dries. You'll notice some small metallic bits in it, cleaned by the engine's oil.

These tips should come in handy, especially if you just rebuilt an engine for your old car. On the other hand, new vehicles are coming from the factory with a break-in process already done. That's why some people say you don't need to do it. But the process is not 100% complete; automakers don't have the time to do that. So, if you want to finish the job properly, you must do it yourself.

Therefore, for peace of mind, you might want to look at these tips.
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