Yes, gasoline has a shelf life, much like any other product.
Heat, moisture and time begin the oxidative process that takes over today's stored fuels, creating gum, resin and varnish.
Today's so-called "clean" fuels typically deteriorate at much faster rates than fuels made 20 years ago. While all fuels suffer from the problem, most at risk are the EPA mandated reformulated gasolines (RFG) that contain oxygenate additives, derivatives of methyl alcohol and ethyl alcohol. Gasoline can have shelf life as little as a month, particularly if it is subjected to heat and moisture.
Diesel fuels may last a little longer, but not much. Most diesel fuels, including the EPA's mandated low sulfur version, has shelf life of from 3-to-6 months. Again, this varies widely.
A shipment of diesel fuel was tracked from a refinery in Texas to its final destination in Florida. It was tested at the refinery the same day it was produced, and the fuel met the specification for stability.
After being stored, pumped into a coastal tanker, offloaded at Port Everglades, stored again, delivered to the fuel jobber, and finally to the customer, 23 days had passed. Again the fuel was tested and the so-called "fresh" fuel now tested out of spec.
In part, this has to do with new processing techniques developed by refiners in recent years. While the new refining methods are more efficient, producing more gasoline per barrel of crude, these fuels are often far less stable than the conventional "straight run" fuels we had before.
To make matters worse, the quality of the crude oil feedstock going into the refinery changes daily with each shipment. Processing equipment must be precisely adjusted to these varying qualities,
but it doesn't always happen. 
This results in poorly processed, less stable fuels. One oil company survey indicates that at least 50 percent of the gasoline sold today is substandard. :eek
Chevron, my employer for twenty years, has some information regarding long-term storage of gasoline:
Longer-Term Storage of Gasoline
Chevron gasoline can be stored for a year without deterioration when the storage conditions are good -- a tightly closed container and moderate temperatures.
Most gasoline is used within a week or two of purchase. But there are occasions when gasoline is kept longer. Examples are gasoline stored to fuel small-engine equipment or to provide a backup supply for a vehicle. Also gasoline left in the tank of a boat stored for the winter or a snowmobile stored for the summer.
Chevron recommends that gasoline not be stored unnecessarily. A supply that won't be needed for several months should be used and replenished when the need reoccurs. Gasoline that is in good condition can be added to the fuel tank of a gasoline-fueled car or truck. (Don't dispose of gasoline-oil mixtures for two-stroke-cycle engines in this way.)
However, when storage is necessary, this bulletin describes how to do it properly and safely.
The term "container" is used collectively for storage cans and drums, storage tanks, and vehicle and equipment fuel tanks except when the discussion is specific to only one member of the class.
This Bulletin addresses:
