Tech Tips: How To Properly Break-In Your Diesel Engine

Breaking in a new engine is crucial if you want years of trouble-free service. For most, trucks are a source of income; a workhorse if you will. Taking the time to make sure everything works properly now will pay off later on.

Much like any other mechanical part, taking a few precautionary measures will save money and potential headaches from becoming apparent later down the road. Improperly seated rings, valves, and oil consumption are just some of the possible issues which can be attributed to an improperly broken-in diesel engine.

Highway & Heavy Parts is dedicated to helping keep your engine on the road for as long as possible, and that starts with properly breaking it in. We have also made a video about everything needed when it comes to breaking in a new diesel engine. Check it out below!


No matter the reason, a rebuilt engine needs a proper break-in period to ensure that everything works as it should. Taking the steps listed below makes sure that you will get countless worry-free miles as time goes on.

Even if your truck is used for play, having the confidence that you can go anywhere is key. Diesel engines are robust, but improper break-in periods can spell disaster later down the road.

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Why Breaking In A Diesel Engine Is Important

Fuel consumption, power production, and even excessive oil consumption can all be traced back to a diesel engine that was not broken in as per the manufacturer's specifications. Taking a few precautionary steps now will prove to be a huge advantage in the long run. 

If you are getting a brand new crate engine be sure to ask if it has already been broken in. A freshly rebuilt diesel engine will also need to be broken in to help make sure everything is working right. Failing to do this can potentially result in you ending up with an engine that is worse off in terms of power and oil consumption than the original defective one. 

What Does It Mean To Break In A Diesel Engine?

The diesel engine break-in process often pushes the piston rings to the block liners. In general, piston rings are intended to apply outward force on the liners, but the force of the gas exerted from the combustion is when they begin to work their magic. 

Here is a photo that better describes how a properly seated piston ring is supposed to work:

Diesel Engine Break-In Graphic

Simply put, oil control rings regulate the amount of oil left on the cylinder wall on the power stroke (no relation to Ford engines). When the engine is not properly broken in, the piston rings will not be able to lubricate the walls properly and may also allow oil to creep past, which increases oil consumption.

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How To Properly Brake In A Diesel Engine? 

Every engine is slightly different from one another, therefore the break-in procedure can vary ever-so-slightly from one to the next. The best plan of attack is to reach out to the manufacturer or the company that rebuilt the engine. This way, no possible damage can occur.

In theory, the best way to break in a diesel engine is to strap it on a dyno so that each parameter like power, RPM, and load can be closely monitored and controlled. Unfortunately, not everyone has a dyno laying around. Luckily, there are options available which allow a diesel engine to be broken in without being strapped onto a dynamometer. 

As a general rule, freshly rebuilt or new diesel engines should be run at idle for the first 10 min and checked for leaks immediately after. High RPMs should be avoided during the break-in process as it can cause unwanted engine damage.

After that, the truck should be run with the heaviest load allowed by the manufacturer to make sure sufficient load is applied to the engine. This step should continue for roughly 100-150 miles. Finally, the truck should be cycled through all the gears and be kept in the highest gear possible at 75%-80% of the max RPM available.

Of course, what we mentioned above is intended to serve as a general guide and specific diesel engine break-in procedures may vary from manufacturer to manufacturer. Always check with the manufacturer or shop before attempting any breaking-in procedures.

Who Is Technically Responsible For An Engine Break-In?

New engines are typically pre-tested and go through a break-in period by the manufacturer, although that's not always the case. For rebuilt engines, it typically remains up to the customer to fully break in the engine.

Rebuilt diesel engines are typically tested and ran to ensure there are no leaks and everything is up to spec. Unfortunately, the labor to go over each step previously mentioned in this article would be far too high, so the rest is left up to the client once they get the truck back on the road.

A reputable shop such as Highway & Heavy Parts will inform you on what the best break in procedure is for your particular make and model. No matter where you take your engine to, make sure the proper engine break-in procedures are followed.


Final Words

Highway & Heavy Parts is dedicated to not only supplying you with the highest quality parts possible for your diesel engine but also providing you with as much necessary information as possible. No matter if you are planning on simply repairing or fully rebuilding your engine, we got you covered! 

Our ASE-certified staff will be more than happy to answer any questions you have about the break-in period of your diesel engine or anything else that you might need to be done on your rig! Call us today at 1-844-985-3408 or request a quote online now!

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