Don't do it. Even in an well-ventilated outbuilding, marked for gasoline storage (ex. bright visible FLAMMABLE GASOLINE label, which may comply with local codes for storage of a *limited* amount of gas, but will defeat any effort to keep your gas cache secret from others), you're still creating a hazard for you, your family and anyone who happens upon your gas. Like most issues around consumption, planning for conservation is better. Buy a cheap bike, start now to reduce your trips, and pretty soon you'll find you're consuming less on a routine basis. If it will take you 100 gallons to get to some BOB location, reconsider your current or BOB location, or your vehicle and its consumption rate.