How Long Does It Take To Break In a Rebuilt Diesel Engine?

We need to stretch our bodies and warm up our muscles before any strenuous physical activity. Following the same idea, you want to break in a diesel engine before putting it through anything too challenging. Ensuring that all your engine components settle in by utilizing pressure and heat is vital in the break-in process.

But how long does it take to break in a rebuilt diesel engine? What do you need to know before putting your rig through anything too taxing? You are at the right place to learn this essential information from the professionals at ATL Diesel.

Starting Up Your Rebuilt Engine

The first vital step in breaking in your engine is to start it up. Let it run for several minutes, and while it’s running, make a few necessary checks. You want to look to see if there are any leaks. Listen carefully to check if there are any peculiar noises like rattles or squeaks. When you connect your engine to your vehicle, examine the dashboard for anomalies. Ideally, you will not find any of these common warning signs.

After these initial checks, your truck should be good to go. Test the waters by driving with a full load but keeping your rig at medium RPMs. The heat and pressure put on the engine from this process are much better at breaking it in than just letting it run idle or dealing with a lighter load.

The Amount of Time for a Proper Break In

The question "How long does it take to break in a rebuilt diesel engine?" is always a reasonably vague, "It depends." It depends on the size of the engine, and also on the vehicle where you install the machine. It depends on how you run it as well, as we already talked about not letting your engine sit and run idly. It even depends on what specific parts you use in the engine, like if you use Caterpillar diesel engine parts or OEM parts.

If you run your engine correctly with proper loading on your vehicle, you should start to notice increased engine performance. You will feel the engine running a lot more smoothly and even increasing the miles per gallon. However, the recommended break-in time for a rebuilt diesel engine is around 150 hours.

For heavy construction equipment and larger semi-trucks, expect a more extended timeframe for this process.

How Many Miles for a Proper Break In

Time is an important factor in making sure all your rebuilt diesel engine parts get to know each other. In the exact same idea, so is getting some miles on your engine. Like time, the answer for how many miles you should put through is "it depends." Critical factors in breaking in your diesel engine are the parts used, the size of the engine, the style of driving, and of course, the weight of the load in your vehicle.

For an initial break-in, which generally happens somewhere between 500 and 1,000 miles, drivers start to notice engine improvements related to the process. A well-maintained engine can show increased performance for as far as 50,000 miles or even more.

What Happens if an Engine Is Not Properly Broken In?

The primary purpose of breaking in your diesel engine is to allow all the parts to "get to know each other." When you do not adequately break your engine in, the piston rings cannot lubricate your engine's cylinder wall; poorly-lubricated walls can result in more oil can sneaking through, which leads to an increase in your engine's oil use. As your engine gets more and more broken in, the pieces fit better together, which leads to better overall performance.

You want the piston rings and oil cylinders to wear correctly against one another. If your piston rings apply an inadequate amount of pressure, problems can arise. These problems range from crosshatch damage to cylinder grazing and even wearing down the cylinder, which can all lead to extra oil consumption.

Failing to break in your engine properly leads to significant problems, such as increased oil consumption, getting fewer miles per gallon, and a noticeably shorter engine lifespan. It is crucial to perform these break-in steps to ensure you get the most out of your engine in the long run.

Performing Oil Changes on Your Rebuilt Engine

Once you break in your rebuilt diesel engine, it is essential to consider oil changes. Because of the break-in process, your first oil change should occur much sooner than the gap between later ones. We recommend changing your oil at around 5,000 miles for a highway truck. It is common for metal debris to get into your oil during the break-in process, which fills up your oil filter faster. Therefore, it is best to get an earlier oil change when starting out. Afterward, a more traditional change every 10,000 to 12,000-mile range is perfectly fine.

Checking with the truck manufacturer or the mechanic who built the engine is a good idea when determining what type of oil to use throughout the break-in process. If your engine uses a traditional roller valve train design, you do not need a special oil when breaking it in.

The timing and mileage of your rebuilt diesel engine will always vary, but these are all excellent tips to keep in mind. Spend the first few minutes checking for any leaks or hazards to make the rest of the process go easier. Keep your engine active throughout the process at a mid-RPM range for the first 500 to 1,000 miles. Keep an eye on the oil filter and change it earlier than average to make sure the breaking in was successful.

There is a lot to remember when breaking in your diesel engine, but following these steps ensures that your engine will run for a good long time. For information on engine parts to helpful hints and service to make sure you get the most out of your engines, ATL Diesel has what you need. Contact us today with any comments, questions, or concerns. You can reach ATL Diesel by phone at 1-866-905-3916 or email us at

How Long Does It Take To Break In a Rebuilt Diesel Engine?