Having built several and run in even more engines the following are my recommendations;

Speak to the engine builder to find out what the clearances have been set to and decide upon a suitable oil to use.

Do not use a synthetic oil while attempting to run in the engine, I would recommend a mineral oil with the least amount of additives.

Warm the engine with gentle driving.

Do not leave the engine idling for long periods of time.

For the first 500km;

vary the engine load and engine speed, do not sit at constant speed for an extended period of time in any 1 gear,

try to keep the revs under 4000 rpm,

try not to use more than 50-60% of throttle opening.

At about 500km change the oil filter and top up the oil to the full mark.

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After 500km begin to work the engine a little harder;

increasing the amount of revs used by about 500rpm for each 100km of driving,

begin to use more throttle opening for short bursts upto the recommended rpm limit for the distance that the new engine has travelled.

By the time that the new engine has 1000km on it it should be run in.

Change the oil and filter to a semi synthetic oil and enjoy driving.

Try to get it on a dyno at a reputable Subaru specialist workshop so that it can be checked for correct afr, that the boost is what it should be etc.

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