Gas treatment

I have read on this forum several boasts about the virtues of Sea Foam as a gas treatment. Well I never used it until 4 weeks ago `when my Snapper lawn mower with Briggs engine started loading up and surging like it was flooding and running rich with black smoke. So I put 1 ounce of Sea foam in the mower gas tank and mowed the lawn, it still ran rough. Repeated the treatment in a week and mowed the lawn. I thought this is not going to work but I tried it again the third week and guess what? It ran smooth all the time I was cutting the lawn. Made a believer out of me. Just takes time I guess. sea foam is going in the MH tank very soon to treat the Onan.