I want to run seafoam through my vacuum line into my plenum chamber to clean out all the crud but I want to make sure that it will not affect my motor oil?
It should not affect your oil. The only way it will if presenting through the intake is if the seafoam got introduced to the oil through leaks in the cylinders/blow-by. It would hardly be enough to do anything anyway, but as a precaution if I would do it again, I would do it within a few hundred miles of replacing my oil again.
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2000 Mercury Grand Marquis LS [ pictures | videos ] Dual Flowmaster Delta 40s / J-Mod / PI Intake Manifold / Marauder Air Box / 80mm MAF CVPI Zip Tube / Ported & Polished Plenum / BBK 70mm / 93 Octane Tune / Steeda Underdrive Pulleys
Combustion chamber cleaning will send something into the crankcase with the blow-by. I don't see it as an issue of merit in terms of wear or contamination. It can throw some unexpected materials into the oil when UOA (used oil analysis) is being used.
Opinions on this vary ..but I do tend to attempt to take any samples before doing any fuel treatments where I'm using UOA. I just want to reduce variables. Otherwise, I don't give it much thought.