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Hey Engine Man – Did I Break In My Diesel Rebuild Properly?

Successful Farming Engine Man Ray Bohacz has engine grease and field dirt under his fingernails from a life spent repairing vehicles and running a farm. When he's not busy in the shop, he's working on maintenance articles and videos for Successful Farming magazine and answering questions from readers. The following is a letter Bohacz received from Justin Clark:

I saw you on the Machinery Show (on RFD-TV) and knew you would be the person to ask about proper diesel engine break-in after a rebuild. I purchased a rebuild kit for my Dodge truck. Per the company’s advise and visits with two of their employees, I was given the following break-in procedure (for proper ring seating / prevention of future oil consumption):

“Once you are ready to restart the engine for the very first time, you run it for no longer than 10 minutes to check for leaks and other issues. If none are found, you immediately hook up to a very heavy trailer and run the truck fairly hard, preferably up and down some hills taking care not to overheat it, for around 200 to 500 miles or so. Then change the oil and filter and drive as you normally do.”

Also, per the two employees I talked to, the preferred way is to break the rebuilt diesel in on a dyno. But I didn't have access.

Other people have also told me to take the truck out and run it as you would normally for the first 500 miles or so being careful to not overdo it. After that, change oil and filter, and then drive as you normally do.

Well, I broke mine in following that advice and after approximately 3,000 miles, I'm using a little oil. I have added around 1/2 quart in close to 4,000 miles.

Since the rebuild, I have purchased several diesel magazines. One had an article that stated diesels are designed to use a little oil (after a rebuild), and that you should not worry about the oil consumption unless you are having to add a quart or more every 2,000 miles.

I'm not sure if my truck is using too much oil. If so, would it be too late to pull a heavier trailer for a while to get my rings seated better?

Response from the Engine Man:

If you extrapolate out your oil consumption – 1/2 quart in 4,000 miles – that would equate to 8,000 miles to a quart of oil. That is EXCELLENT!

If you would have spoken with me a year ago, I would have suggested the procedure that you did follow. Change the oil shortly after it is on the road and then drive it normally. I would also refrain from short-trip cycles and numerous warmup cycles or excessive idling.

But if this is how you normally drive, then I would have suggested going on a long highway trip before subjecting the rebuilt engine to short duty-cycle use.

There are also many things that need to be considered regarding an rebuilt engine break-in. These include:

• The ring type employed and, more important, the cylinder wall finish.

• The "normal" use of the engine.

• What exactly was done for machine work.

Have a maintenance question? Email Bohacz at





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