Fuel Volatile and our Classic Cars.
By George Potter
While on the “Oregon Adventure CARavan” I noted a
problem that many of the CARavaners were experiencing
or worried about “Vapor lock”. Most were
convinced that the high volatility of the fuel was a
result of E10 (Ethanol fuel) and were looking for (Clear
Gas Non- Ethanol fuel) stations. One of the tour
participants commented that he used only premium fuel as
it had less volatiles.
Hmm all sounded interesting and being one of those who
wants to know for sure I decided to do a Google search.
My search “is premium gas less volatile”. Wow
pages full of answers, all saying yes premium was indeed
less volatile and a lot of other information concerning
our modern fuels.
The articles all agreed that
the higher the octane rating on fuel the less
volatiles (evaporative qualities) it has and to
us that means less vapor lock. The engine
runs best with a slow even burning of the fuel. Octane
ratings are an indication of the burn or flash rate of
fuel. The higher the octane rating the lower the
volatiles and the slower it burns. Now it makes sense to
me, high octane fuel has fewer volatiles to slow the
burn rate and fewer volatiles means less vapor lock.
There’s lots of information attesting to the bad side
effects of E10 fuel when used in our old cars. A couple
of reasons for avoiding it is that it is an excellent
absorber of water that then condenses out in our tanks
and fuel system. It is a solvent that damages gaskets
and any rubber parts in our fuel systems. Interestingly
I could not find any information indicating that adding
Ethanol actually increased fuel volatility.
So my conclusion, the CARavaners were correct in using
Clear Gas or Premium fuel. Clear Gas has to be the first
choice because Clear Gas is high octane and
non-ethanol thereby reducing vapor lock and the
damaging effects of Ethanol. If Clear Gas is not
available the next best option is high octane premium
In my Google search I found a website listing gas
stations that have Clear Gas (non Ethanol fuel). The
Historic Vehicle ASSOC.
Here are some on the other highlights of my fuels
The logic is that since
it is a premium fuel it must be better. In
label originates from
the higher cost to refine and the resultant higher
retail cost. It is reasonable to assume that premium
fuel is the same as high octane fuels.
Some owners think that these
fuels will make their
more powerful. This is
a MYTH! Only engines with high compression
ratios, 9.3 or more, can deliver all the potential
energy from higher octane fuels! In fact using
Premium in low compression engines will result in a
slightly reduced HP and MPG,
Modern engines, 1990 and later will safely burn 87
octane even with a higher compression ratio. This is
accomplished by the engine fuel/air
management/timing system in modern cars adjusting so
as not to cause pre-detonation (ping) in the engine.
The storage life of fuel is one year when stored
under shelter in a sealed container. Once a seal is
broken the fuel has a storage life of six months at
65 °F, or three months at 85 °F. If stored in an
open container or fuel tank, the storage life
is reduced to one month. And now we know why we add
fuel preserver to our tanks……