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Diesel Engine Break-in Tips & Tricks

Diesel engines are known for their durability and longevity, but even the most robust engines need to be properly broken in to ensure optimal performance and longevity. Breaking in a diesel engine involves a process of gradually increasing the engine's workload over a period of time to allow the engine's components to wear in properly. In this article, we'll explore the importance of breaking in a diesel engine and provide some tips on how to do it properly.

Why is Breaking in a Diesel Engine Important?

Breaking in a diesel engine is essential to ensure that the engine's components are properly seated and that the engine performs optimally throughout its life. During the break-in period, the engine's components, such as the pistons, rings, and bearings, are still adapting to each other, and it is crucial to allow them to wear in gradually. If you skip the break-in period, you may experience reduced engine performance, higher fuel consumption, and more significant wear and tear, which can lead to engine damage.

Diesel Engine Break In

How to Break in a Diesel Engine

Breaking in a diesel engine requires following specific steps to ensure that the engine's components wear in correctly. Here are some essential steps to follow when breaking in a diesel engine:

Follow the Manufacturer's Recommendations
Before breaking in your diesel engine, read the manufacturer's recommendations in the owner's manual. Different diesel engine brands have varying break-in procedures, and it is crucial to follow the manufacturer's guidelines to ensure optimal performance.

Avoid Idling
When starting a new diesel engine, avoid letting the engine idle. Keeping idle time to a minimum, and operating a freshly rebuilt engine at 75% of full load for at least the first 3 to 4 hours, produces satisfactory results in getting piston rings to seat. Doing this allows the engine's components to adapt to each other, reducing wear and tear.

Vary the Load and Speed
During the break-in period, vary the engine's load and speed frequently. Avoid running the engine at a steady speed for extended periods, as this can cause uneven wear in the engine's components. Varying the engine's speed and load ensures that the engine's components wear in evenly.

Monitor the Engine's Temperature
While breaking in your diesel engine, it is crucial to keep an eye on the engine's temperature. The engine's temperature can increase significantly during the break-in period, so make sure the cooling system is working correctly, and the engine does not overheat.

Specific Diesel Brands and Break-in Recommendations

Different diesel engine brands have specific break-in recommendations, and it is crucial to follow them to ensure optimal performance. Here are some examples of break-in recommendations from specific diesel engine brands:

Cummins
Cummins recommends a break-in period of 500 miles for new diesel engines. During the break-in period, Cummins recommends varying the engine speed and load frequently and keeping the engine's temperature below 220°F.

Caterpillar
Caterpillar recommends a break-in period of 50 hours for new diesel engines. During the break-in period, Caterpillar recommends running the engine at varying speeds and loads and monitoring the engine's temperature regularly.

Detroit Diesel
Detroit Diesel recommends a break-in period of 500 miles for new diesel engines. During the break-in period, Detroit Diesel recommends varying the engine speed and load frequently and monitoring the engine's temperature closely.

Breaking in a diesel engine is essential to ensure that the engine performs optimally throughout its life. Following the manufacturer's recommendations, starting slowly, varying the load and speed, and monitoring the engine's temperature are all essential steps when breaking in a diesel engine. Specific diesel engine brands have specific break-in recommendations, and it is crucial to follow them to ensure optimal performance.

Breaking In Rebuilt Diesel Engines

Even with quality replacement parts and engine assembly, you can still have problems with oil consumption if the engine is not broken in correctly to get the piston rings to seat. 

Rings are designed to apply a certain amount of tangential force outward. Compression rings rely on greater combustion pressure to force them down against the bottom of the piston’s ring lands and outward to the cylinder wall. Without this combustion force, these rings may not seat or seal properly. Oil control rings regulate the amount of oil film left on the cylinder wall to lubricate the compression rings, and each compression ring removes some amount of this oil film resulting in proper oil control. 

While it is ideal to break an engine in under a controlled environment (such as a dynamometer test where load factors, horsepower, temperatures, etc. can be controlled and monitored), it is simply not always an option available after a repair or rebuild. That’s not to say you cannot get piston rings to seat without such equipment, but it is important that an adequate load be put on the engine to create enough combustion pressure and temperatures to seat the rings. This is most critical within the first few hours of the engine’s new service life. Idling, increasing the RPM, and hauling light loads will not create enough combustion pressure to seat new rings. Only under load can you obtain the pressure and temperatures needed. 

We have not found an OE publication that formally details the process for breaking in an engine outside of a controlled environment to reference, but our research has found that keeping idle time to a minimum, and operating a freshly rebuilt engine at 75% of full load for at least the first 3 to 4 hours, produces satisfactory results in getting piston rings to seat.

The percentage of load and duration may change from rebuilder to rebuilder (many already have a proven process for engine break in). All agree that once the initial start-up and checks are complete, getting a load on the engine is vital to seating the rings. Delaying this loading process can result in increased oil consumption. 

Notice: Approved Lubricants
The brand, type, classification, and oil grade used during an engine break-in period can affect the piston rings performance. Use of OEM recommended oil is preferred. There are also several additives and break-in oils available. Those should only be used according to the manufacturer’s recommendations.
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