Well, I just meant that seafoam is more of a solvent than an oil. Smell it, it smells to me like carb cleaner. It works as well as carb cleaner for cleaning parts too. It may do no harm being left in. Also see what the oil pressure is in the morning once it has cooled down. It should be high again. It also could have been a sticky relieve valve, or the drain back valve in the oil filter or.....

-Tad