I was researching fuel oil tanks because I need to replace mine and I came across this article about fuel storage.http://theepicenter.com/tow021799.html
Foe example, here's a quote from the article:
"The problem begins with today's modern fuels. These 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. We've seen gasoline have shelf life as little as a month--particularly if it is subjected to heat and moisture.
Diesel fuels fare a little better, but not much. Most all diesel fuel, including the EPA's mandated low sulfur version, has shelf life of from 3-to-6 months. Again, this varies widely. Recently we tracked a diesel fuel produced at a refinery in Texas to its final destination in Florida. When tested at the refinery the same day it was produced, the fuel barely 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. This "fresh" fuel now tested out of "spec."