G. Wall of Guilford, CT, asks:

There's been a lot written about the dire effects on Diesel engine life by running with too little load. Varnishing of cylinder walls is mentioned. Do you or Lugger feel that running at 1400-1600rpm and only using a fraction of rated HP is detrimental to engine life?

Dan Streech responds:

We are often asked this question although usually in the context of generator loading.

The key point on this subject is the initial break-in procedure followed when the engine is new or has been rebuilt. The break-in process mainly relates to the proper seating of the rings.

Alaska Diesel Electric (Lugger) gives detailed instructions in their owner's manual for the proper break-in of a new engine. The highlights of the instructions for operation of the engine during the first 100 hours are:
1. Do not run the engine at 100% power for more than 5 minutes at a time. This is due to a     concern about excessive heat on a tight new engine.
2. Run the engine at 50%-75% power output. This keeps the rings expanded and in firm     contact with the cylinder walls so that seating can take place and glazing is avoided.
3. Avoid long periods of sitting idle speed. This is self evident when one understands the     logic of item #2.

Once the proper break-in procedure has been completed, it is not harmful to run the engine (or generator) at low power settings.

Personally, I like to "blow out the soot" from time to time when running at low power settings on a long passage by running at maximum power for a few minutes every day or so. This isn't called for in the manuals as far as I know, but it makes sense to me.

As a footnote: Several days ago, I answered a question about the use of synthetic oil. I can't remember if I have read it anywhere, but I have heard several old-timers say that one should avoid the use of synthetic oil on an engine during the break-in period because the reduced friction will jeopardize the ring seating process.

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