Cummins' Break-in Recomendations

[bighammer]

What is the recommended break-in procedure for my new Cummins engine?

Cummins does not publish a specific time or mileage threshold that provides when an engine is considered to be broken-in since our engines are used in such a variety of applications and purposes. Here are some general guidelines to consider when breaking-in your new engine:

INTIAL BREAK-IN PERIOD = 1000 miles or less. During this period, the piston rings may not have had a chance to seat yet, which allows cylinder pressure to pass by the rings into the crankcase, causing blowby. After the initial break-in period, the engine will need to be worked to create high enough cylinder temperature to seal the piston rings, which helps prevent blowby.

Vary the engine speed so the entire vehicle, as well as the engine, becomes accustomed to varying speeds, loads, rpm, etc..

For on-highway, automotive applications, operate the engine at 1500 to 1800 rpm in high gear for the first 50 to 100 miles. However, DO NOT idle the engine for more than five (5) minutes at any one time during the first 100 miles.

For off-highway, non-automotive applications, operate the engine at 75% throttle while loaded during the first three (3) hours. Again, DO NOT idle the engine for more than five (5) minutes at any one time. Also, DO NOT operate the engine at rated speed (rpm) and full load for more than five (5) minutes at any one time.

MID BREAK-IN PERIOD. After the first 1000 miles, the engine is ready to be worked, which will help seat the piston rings to avoid blowby and avoid carbon buildup to avoid fuel slobber because of light load operation. If possible, drive in hilly or mountainous areas OR load the truck with 700 - 800 lbs OR pull an empty trailer (tandem car-hauler type)*.

*NOTE: If you use a small single axle trailer, some load on the trailer is recommended.

Certainly everything with a new truck will 'loosen up' after 40 or 50k miles, including the engine, wheel bearings, brakes, etc. etc. We doubt that the engine torque or power will increase much, however. With light loading, the engine can take as high as 30,000 miles to be considered 'broken in'.

When the bearings, brakes, engine, etc. do 'wear in', the truck may seem to perform better, just because you will have less resistance from all these new components. The amount of fuel consumed by the engine may improve slightly after the break-in period, however, there are many other variables involved with the vehicle chassis that will affect MPG, more than the engine.