jJim McLaughlin wrote:
dpb wrote:

jJim McLaughlin wrote:

Steve wrote:

Have a 10 year old Troy Bilt. It has always started on the 3rd
pull. Saturday I mowed my front yard, then then Sunday it started
fine, but I ran out of gas. Filled it up and it won't start now.


That gas you put in was new fresh gas with Stabil or such in it I
hope. Surely you didn't
uselast years gas.


Last year's gas, other than being just a little harder starting
initially, is just fine...

No, its not. You have no idea what you are talking about.

Well, let a manufacturer talk...

Unless the gasoline is stored in a hot environment and not a closed
container, since gasoline blends have anti-oxidants and stabilizing
additives in them to begin with, the problem is not particularly severe.
While it might be "good practice" to drain an engine over winter, not
doing so isn't a major issue, particularly over winter months. Small
engine manufacturers recommend the practice mostly as a conservative
practice.

From a manufacturer (Chevron in this case)...

"The gasoline light ends needed for easy starting have the same tendency
to vaporize in storage as they do in an engine. _If_ the storage
container is not tightly sealed, _some_ of the light ends gradually will
be lost. Too great a loss decreases the gasoline's ability to start an
engine.

.... keeping the container almost full of gasoline and controlling the
temperature fluctuations will minimize the loss of light ends, the
exposure of the gasoline to air, and the contamination of the gasoline
with water.

Oxidation

Except for any added oxygenates, gasoline is made up almost entirely of
hydrocarbons–molecules constructed from the building blocks of elemental
carbon and hydrogen. _Hydrocarbons, as a class, are chemically stable
molecules_.

However, there are types of hydrocarbons (olefins and diolefins) that
can combine slowly with the oxygen in the air ("oxidize") at ambient
temperatures. The products of the reaction are larger molecules,
collectively called "gum."

The gum-forming reactions become faster as the temperature of the
gasoline increases. This is why this bulletin recommends controlling the
temperature of stored gasoline.

Most gasolines contain negligible amounts of gum when they are
manufactured, and most contain special chemicals ("stabilizers") to
retard gum formation. It is the stabilizers that make it possible to
store Chevron gasolines for a year when the conditions are good.

Soluble Gum
....
Because the Federal Environmental Protection Agency recognizes that fuel
system deposits increase emissions, they require all gasolines to
contain a deposit-control additive. All deposit-control additives keep
deposits from forming; ...

Other Issues

Storage, including storage involving gum formation, does not change the
bulk properties and most of the performance characteristics of gasoline
(excluding the characteristics affected by the gum itself). For example,
storage does not change a gasoline's anti-knock index (octane) or energy
content. However, these properties will change if the storage is
accompanied by evaporative loss. The evaporation of light ends decreases
a gasoline's antiknock index and increases its energy content.

Federal and California reformulated gasolines will survive storage as
well or better than conventional gasolines. The regulations require
reformulated gasolines to have less light ends and less olefins
(federal, later; California, now) than conventional gasolines. As
explained above, it is the oxidation of olefins that leads to gum
formation. Reformulated gasolines also contain oxygenates. The common
oxygenates are stable molecules that do not form gums."

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