I would not use it at all that way. if you're really gung ho, then
use auto rx, which works wonders, or use MMO, which doesn't do that much, but it's not too dangerous either (put in for one or two weeks, or 500 miles, before draining), or drain a quart of oil and replace with diesel fuel, and idle for 10 minutes and drain. or drain all oil, replace with diesel fuel, and let sit overnight, crank engine with ignition wire disconnected, and drain, and change the oil once again within a few days of doing this. seafoam is too strong of a solvent to go into a crank case - your engine will suffer accelerated wear, and you will end up with a very clean worn out engine ready for rebuild.