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This is really simple.
If you use a sealed bearing, it must be lubricated internally period.
On the other hand, if you use an unsealed bearing, you remove the outer seal to allow oil to lubricate it. The LN Retrofit experience shows that splash oil from the sump is sufficient for the unsealed ceramic bearings to last well beyond 50,000 miles before considering a replacement.
Whether you add DOF or not, you do not remove the inner seal. If you do, oil will accumulate in the IMS tube.
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