by far sta-bil marine (blue) for me. ALSO, a shot of seafoam at the beginning of the season, another shot 1/2 way thru the season for me. have had fuel in the boat, lawnmower, weedwhacker, ice auger, snowmobile, quad, etc over 6 months old and started right up. the red sta-bil gets gummy and doesn't keep the ethonal from seperating. haven't found anything better so far.