Millers Running-in oils should be used for the first 500 miles after which the filter should be changed and the oil should be replaced with an appropriate engine oil.  We have the following 2 running in oils:

Classic Running-In Oil (SAE 30): for initial running-in of re-built engines.  This product is formulated for running-in on the road but it can also be used for test-bed running-in.

CRO Competition Running-In Oil (10W40):  for test bed running-in for up to 4 hours. Can also be used for light operational duties up to 500 miles.  This is an advanced formulation which meets the needs of the professional engine builder.