Shelf life is a BIG factor. 6 months without an additive like Stabil. I don't know with. Someone mentioned the locale that this gas came from and someone else mentioned time of year it was bought. Both have valid points. If you look at a county by county map of the U.S. most of them have their own standards of the blend of gasoline they can sell. Gasoline is a blend of different hydrocarbons. High smog area demand different blends that low or no smog areas don't. Time of year and location affect the volatility of the blends. Cold weather needs lighter blends, say more butane than a summer blend in the same area. With all of that said, this is for your sensitive electronically controlled, fuel injected auto, not you low tech carbureted gen set. Once those volatiles evaporate/condense out you still have a burnable liquid. In the old days varnishes were a big deal, they are what gummed up the lawnmower that you didn't drain the fuel out of for the winter. They are still there, but gasoline is way more refined and cleaner now, but still may present long term >1 year storage problems.
On safety. Liquid gasoline doesn't burn, the vapors that have mixed with oxygen does. A full tank is pretty safe. Now if it leaks, then what leaks out is a problem, or if you store gasoline in your garage and fire breaks out there, once the container bursts or is compromised then that will literally add fuel to the fire. Most of the time it won't explode like in the movies, but flare out. Not much difference if you are standing close by. Buried tanks would be a good way to go, except if they leak and you care about it getting it in the water table or the environment in general.
My dad and I were putting a new driveway in next to the house and our yard was mostly sand. About 30 feet down then blue clay. Well this was 1978 and we put two 400 gallon of those oval heating oil tanks in buried right up against the foundation with the fill tube sticking up out if the ground. Back filled them with sand and had the contractor do the pour. Filled them with gasoline. A couple years ago we got some out to see what was up. It was cruddy, but it burned. Not sure I would run it through a genset though. In retrospect, pretty dumb of us, but I claim being fourteen exempts me
Diesel has a longer storage life, about two years, and is less volatile. Burns, but it takes some doing. Rule of thumb. The more refinement it needs the harder to store for a long period of time.
Look at this thread we have going here.
http://mutuallyassuredsurvival.com/smforums/index.php?topic=641.msg2201#msg2201 Merits of propane vs gasoline and diesel. This is to quote Ryder "The nice part about propane is that the fuel will store for a long long time." Forever really. It isn't a blend of hydrocarbons like diesel and gasoline it is only one hydrocarbon. It has three carbons with all of the covalent bonds taken up by hydrogen.
http://en.wikipedia.org/wiki/Image:Propane-2D-flat.png Read the wiki on it.
http://en.wikipedia.org/wiki/Propane. If you read the above thread you will notice I converted a Generac gasoline to tri-fuel. My house had natural gas, but before Y2K I had a 500 gallon propane tank installed. Yes they looked at me screwy, but that was piped to my generator and a vent free natural gas log in an antique open face fireplace. I had wood heat too.
The other thing one may want to think about is diesel, but instead of storing lots of petroleum diesel, make biodiesel. You could go to Tractor Supply or Orshelin's and get one of those big 1000 gallon stock tanks and go around to restaurants and collect their waste oil and store it in the tank. Make the fuel as needed. I won't go into the collection of WVO, please do the research, because if you just drive up to a grease bin and start pumping, you may end up in jail. Just a thought on the diesel. I'm biased
