Having been through more than a few hurricanes that caused power outages and fuel shipment delays, I would like to post some information about fuel preservatives.
First, because I am cheap and willing to admit it, I do not add fuel preservatives to every can of fuel stored. I have a supply of fuel to run the generator and the car for four days. This is what I consider fresh fuel. I rotate this fuel through my car after a short period of time. I use it in yard and lawn equipment. I replace it regularly and watch for the weather reports. At the first sign of a pending hurricane episode, I fill up the car and all the fresh tanks. This fuel is used before it needs any preservative or stabilizer.
Sta-bil is made by STP and is available at any auto parts store. It is also offered at large retail home building supply stores. You can look online for it's statistics and it's virtues. Shop for it in person. If you 'have a guy' at your local hardware store, you can have him order in some extra. STP offers a stabilizer for gas, diesel, and marine fuel, as well. I have used Sta-bil. It does the job. The fuel stored for the generator over the winter months is safe and stable.
PRI-G for gasoline and PRI-D for diesel actually addresses those who wish to be prepared on their website. They address the need for a dependable fuel for emergency generators and equipment. Click here, http://www.priproducts.com, then click on their link to dealers near you. Their first clients were mid-sized marine industrial vessels. The reviews I have seen show no bias toward the marine industry. I went online to find a dealer near me. There is no dealer near me. I have to drive 35 to 40 miles to buy PRI-G. Soooo, if I am feeling it in three weeks (I have plans) I will decide do I want to go fresh water fishing or salt water fishing. If you have been paying attention, two things: 1) I live in Florida and 2) I will combine activities when there is a trip involved. If I decide to go fishing, I won't be able to review the product personally for a year or two.
Before I sign off for this evening, allow me to add that fuel storage is more than chemical stabilizers and gas. You must always keep safety in mind and never forget that gasoline is dangerous when stored or used improperly. Always store in containers or tanks approved for the storage of gasoline. Keep it cool, dry and secured from minors or strangers. Do Not store fuels in the home or an attached shed or garage. Fire happens, don't be there if it does. Stay safe, be smart.