You can leave Sea Foam Motor Treatment in the oil for as long as you’d like.
However, we recommend adding Sea Foam to oil 100 to 300 miles before the end of each oil change interval for two reasons:
that gives it time to circulate and clean as you drive
that allows all the residues that were reliquefied by the Sea Foam to be drained away with the dirty oil. It is safe and fine to drive for as long as you want with Sea Foam in the oil, but the oil will likely become dirty as the Sea Foam cleans, especially in an old/dirty crankcase.
You can leave Sea Foam Motor Treatment in the oil for as long as you’d like.
However, we recommend adding Sea Foam to oil 100 to 300 miles before the end of each oil change interval for two reasons:
Hope that makes sense!