Join Date: Feb 2007
Location: San Diego, CA, USA
Gasoline degrades continuously during storage primarily because of evaporation of the more volatile components (leaving a waxy varnish-like residue), chemical breakdown, and oxidation. Sunoco racing fuel, for example has a shelf life of about a year, if you leave it stored sealed in its original 55 gallon container. Higher storage temperatures will reduce the allowable storage time.
Pump gasoline is formulated differently than race gas and will deteriorate noticeable in about a month. Gas in a four gallon tank will often be still usable after six months. The greater the volume of stored gasoline, the longer it will remain usable, and the smaller the amount stored, the sooner it will break down.
It's an issue of dilution and evaporation rate, which means that the gas contained in a bike's SEALED gas tank remains usable longer, but the small amount of gas that is in your fuel line or vented float bowls, etc. will degrade more quickly during storage. Fuel injected motors have fuel lines that are sealed to the environment, so fuel evaporation is not the major concern, itís chemical breakdown which takes much longer.
So, for gas in unsealed containers or older bikes with vented fuel tanks or carburetors, you especially need to use fuel stabilization treatments (i.e. Stabil) during storage.
Most important, you need to run the engine before storage to insure that the stabilized fuel reaches everywhere in the system.
If youíve filled the tank a couple of months ago, but forgot to use a fuel stabilizer, put some in now and just run the engine to purge the old fuel from the lines.