It isn't going to blow up for being 80 degrees. In fact it wouldn't blow up until it reached 150 degrees and then introduced to a flame:
"Cool or cold No. 6 fuel oil is surprisingly stable. Don't try this at home, but a burning match or a shower of sparks would probably not be sufficient to ignite the fuel oil. On the other hand, when No. 6 fuel oil is heated, problems can arise. Flashpoint is defined as the temperature at which a liquid gives off enough flammable or combustible vapors to sustain a flame.
The flashpoint of No. 6 fuel oil is approximately 150 degrees Fahrenheit. If the vapors mix in the correct proportion to air, an ignition source as small as a stray welding spark can cause a violent explosion. The tanks blow up when flame from an accidental ignition source traces a path of vapor up into the empty space in a tank.
This headspace is actually filled with flammable vapors if the contents of the tank are above their flashpoint. No. 6 fuel oil is a complicated mixture, and it sometimes contains hydrocarbons with flashpoints significantly lower than 150 degrees. For this reason, No. 6 fuel oil will sometimes give enough flammable or combustible vapors to start a fire when the oil is stored at ambient temperatures. When these vapors burn inside the tank, they produce enormous pressure.
Such explosions have been known to tear storage tanks off their foundations, causing oil-spills and expensive fires."
Gasoline is a bit different:
"The most commonly known flammable liquid is gasoline. It has a flash point of about -50° F (-65° C). The ignition temperature is about 495° F (232(232° C) [sic], a comparatively low figure."
That means that unless you light a match and throw it on the barrel, the gasoline is not going to explode. Now degradation factor is different:
http://home.aol.com/keninga/fuel.htm
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