I ordered some of the Gas and Gas Plus additives. I'll try the Gas Plus in the boat, and the regular Gas additive in my 4Runner and Corolla. It looks like a great stabilizer for the boat. I'll see what happens in the vehicles.
An 8 oz bottle treats 25 gallons. A 3 x 8oz pack is $27 and treats 75 gallons. It cost $0.36 to treat a gallon of gas. I would have to see a +10% increase in MPG to justify running this in my vehicles. Just to compare, FP60 starts at $0.094 to treat a gallon. Buying either product in volume brings down the cost.
Sentry may be more for stabilizing gas than a regular use additive.