not good

seafoam is an oil additive that breaks up all the varnish and sludge. i have heard of putting diesel in the oil and running it like that for a short while. it breaks down all the crap inside the engine and breaks it loose. if you do either i would buy 2 or 3 filters (cheaper ones) and run it for like 10 min then change the first one then maybe half hour and change the oil completely and put new filter on.