For fuel stock-pilers -- Amz has STA-BIL 360 Marine Formula on sale for $8.00 for 32 oz, treats 320 gallons of fuel. It's a combined ethanol treatment and fuel stabilizer. Although "formulated" for marine use, it is reported to work fine in autos, trucks and small engines.
ETA: Price drops to $6.80 if purchased with Subscribe & Save.