Startron, little blue bottle, available at Wal-Marks, is cheaper per gallon treated and also does an excellent job. It only calls for an ounce per 16 gallons. The little bottle lasts a long time for me. (Just did the math, 8 oz bottle does about 130 gallons.)
I have gotten where I put Startron in all my gas whether for the boats or in the gas can which will eventually make it into my lawn equipment or chainsaws or tractor. Cheap insurance when you aren't really sure how long it will be before you use that gas up.
Seafoam works well too but is much more expensive.
http://mystarbrite.com/startron/