Thread: I made the mistake.

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My understanding is, you should not use synthetic oil for the breakin period of the motor (use the breaking oil recommended by the motor builder), as synthetic oil may not allow the rings to seat properly, causing excessive oil consumption (blow by).

If you have not run the motor, you should be able to just drain the oil and replace the filter (save the oil and filter), install a new filter and fill up with breakin oil. After the breakin period, change the oil using your recovered synthetic oil for a short period of time, then replace with new oil and filter.

However, you may want to run conventional oils with additives for a little longer than the breakin period (see your motor builder for recommendations), to assure everything is mated properly before using synthetics.