We will generally think of gasoline fuel for storage, however, gasoline DOES NOT store well. In fact, have you have ever made the mistake of putting your lawnmower away in the fall with gas in the tank and then trying to start it the following spring? Do you know that the service mostly consisted of cleaning the stale gas, gum & varnish out of the carburetor, and putting fresh gas in?
Forget the car gas tank as a source. This will prove to be the ONE TIME that the car is nearly empty, and besides, have you ever tried to siphon gas out of a modern car with all those vapor traps, and emissions things. It will prove to be nearly impossible!
So, we need a supply of gas that is NOT in the generator's or car's tank. How much?
Fuel Storage Discussion (For a Generator)
Well, if "survival unassisted for 72 hours" is to be the yardstick, how many hours out of that 72 will you be actually running the generator? Remember that the fridge will STAY cold if you can run it a few times a day for an hour or so each time, ditto the freezer, and the furnace fan won't have to be on all the time either. During daylight hours, you don't need lights, and you might want peace & quiet at night, so I suspect that a total of about 5 - 6 hours per day should do, but let's assume (for this example) a total of 8 hours per day. What is the real (actual) fuel consumption of your generator, (gallons per hour) times 8 hours per day, times 3 days. A "2 gallons per hour" machine will need to have 2 X 8 X 3 = 48 gallons on hand!
(RE-THINK! Do we really need a generator THAT big!)
Maybe we can get by with one a bit smaller. Maybe 2 small machines, a teeny (500 watt) one for "continuous" run, and a 2250 watt beast to power a circular saw etc, for emergency repairs. The big guy needs a gallon an hour, so we would need to have at least 24 gallons in storage in the above example, while the little one may drink as little as 8 or 12 gallons in total. I would suggest about 20 gallons as a bare minimum--enough to run the little one for a long time, with reserve fuel for the bigger one as required, or conversely, a reserve of fuel should a longer period of self-sufficiency be required.
There is a product out there called Sta-Bil or PRI-G. They are is a fuel stabilizers, and it is supposed to prevent gas from breaking down. USE IT! It is available at many hardware, "big box" home supply stores, automotive stores and places where mowers and chainsaws are sold. But don't keep the gas around forever. Just as with everything else, rotate your stock.
Gasoline is probably the easiest fuel to rotate because we use so much of it in our autos. I suggest keeping several 5 gallon gas cans full, and also ensure that you don't keep any one of them more than 6 months. Simply rotate the stock, by putting the oldest gas into the car, and refilling the gas can at the service station, adding fuel stabilizer each time. If you only need to have 12 gallons on hand, get three 5 gallon cans (15 gallons total), and once a month put one into your car, and then refill it, putting it at the back of the row. Next month, put the next one in, etc. If you "rob" your supply to fill the lawn mower, that's fine, too, just make sure you keep minimums on hand.
DO NOT KEEP THE GAS IN THE HOUSE!
The garden shed, the "pallet root cellar", the garage (only if it is not attached to the house) or wherever else is fine. NOT in the house! Gasoline is DANGEROUS.
In case of earthquake or whatever, there is a risk of fire. Do you want to have 15 or 20 gallons of highly explosive, extremely flammable stuff in your house? AND, What happens in case of a "normal" house fire?
On a final note: A small, 1 or 2 gallon gas can should be kept handy for filling the generator's tank. It is easier to manage than the 5 gallon size for filling the relatively small tank on the generator. At my house, my wife is physically not large enough to handle the 5 gallon size with any accuracy, but I or she could use one of the big ones to fill the smaller can, and then she gases up the generator with the little can, should anything happen while I am away. The little can won't go to waste--use it for your ongoing supply of lawnmower gas!
On a related topic, get another one-gallon can, and a bottle of 2-stroke mixer oil as well. Again, do not keep a can of mixed fuel around--it will deteriorate, but your chain saw (you DO have one, don't you?) will also need to be fed, and will be invaluable for getting those downed trees out of the way or off the house. Mix the fuel only as required, so you will keep it fresh as well.
Give the generator's engine the occasional oil change. Once a year should be fine unless you are using it a lot. Oil, like fuel, deteriorates over time (and use) as well as attracting contaminants.
Figure out your needs, get the gas in convenient, easy to use sizes, use a fuel stabilizer, rotate the stock, and store it securely away from the house. Now your emergency, standby generator might actually do some good!
Some interesting sites.