I've been googling diesel run in, and generally encounter two opinions:

  • The first is treat it gently for the first 1000k, and do not exceed 2,000 rpm.

  • The second is drive it at 3/4 revs, maybe 2,500 to 3,000 revs depending on the engines operating range. And don't treat it gently, apply load and get the engine working as hard as you can within this range.

Who is right and why?

I should add the particular engine I am thinking of is my Toyota 3L from 1992, just re-built. Its a straight 4, no turbo. But I'm also interested in general about diesels including more modern ones.

1 Answer 1


For any engine, no matter petrol or diesel during the RUN IN period it should be driven gently and not aggressively for the first 100 or 150 miles after that it should be a combination of aggressive and passive driving.

  • The first 100 or 200 miles of an engine is delicate since the components will not be used to the levels of stress and being aggressive in this phase regardless of being a petrol or diesel engine is not advisable
  • After this interval you need to run the engine mostly at its peak torque range and sometimes fluctuating over and below the peak torque rpm.

To answer your question, its the combination of both, drive gently for the first 100 or 150 miles , after that apply various loads and fluctuate RPMs to get the engine broke in.

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