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 Some
concerns have been raised recently about the use of ethyl alcohol, or
ethanol, in petrol. The product
added to petrol may also be called bio-ethanol to link its use with
non-fossil derived or renewable buo-fuels.
Bio-ethanol has been used at times over the decades, but its recent
use is linked to EU directives to increase the proportion of automotive fuel
derived from renewable sources, in order to reduce carbon dioxide (CO2)
emissions.
Ethanol
has been blended into petrol in recent years by, among others, Tesco, who
use it in their premium 99 octane unleaded petrol blend.
Ethanol has a very high octane quality, and so is a valuable blending
component for use in the production of high octane unleaded petrol.
Its use in this application is limited to 5% volume and is
acknowledged by a label on the pump according to the Tesco help line,
although this may not always be the case.
Although the EU is believed to be considering the mandatory use of
bio-ethanol in petrol in the future, at present it is to be hoped that
classic vehicle owners would not encounter the blended product without some
form of pump marking. If any
owners have concerns over using petrol containing 5% ethanol, it would be
useful to check fuel before purchase by inspecting pump labels.
Concerns
expressed have centred on possible water contamination, degradation of
plastic and rubber seals and possible negative effects on foams used in
racing tanks to prevent fuel fires and explosions.
The position on these issues is not straightforward and is still
being investigated in order to establish an accurate understanding.
Also, as the proportion of ethanol in the blend is increased, so any
difficulties are more likely to become apparent.
Although
the 5% ethanol blend can give higher octane quality, volatility is also
likely to be higher for this blend of fuel.
Some owners are already troubled by driving problems associated with
high volatility (vapour lock, fuel starvation, bad hot starting etc. in hot
weather), so using a 5% ethanol blend could make such problems worse.
The
following report gives a more detailed picture of the likely effects of the
use of ethanol-petrol blend fuel.
Aspects
of the use of petrol containing ethanol - Based on
a recently published public domain document, CONCAWE Report number 3/08
Fuel
volatility
Blending
small amounts of ethanol (up to 5%) into petrol does produce a measurable
increase in volatility. Oil
companies must ensure that fuel volatility meets specified limits (EN 228)
so petrol containing ethanol will be adjusted to this specification. However, if fuel containing ethanol is mixed in the vehicle tank with
purely hydrocarbon fuel an increase in the volatility of the blend in the
tank can result. This may
produce unwelcome
symptoms
of poor hot starting, erratic running including running too rich, or too
lean, associated with excessive fuel volatility. The FBHVC caters for a wide range of vehicle ages, and it is highly
probable that some will be less able to cope with an unintended increase in
fuel volatility, and also some time-related deterioration in performance of
cooling systems. Unfortunately,
it seems that not all fuel containing up to 5% ethanol is labelled as such,
so the scenario of mixing two types of fuel in the vehicle tank is a
realistic one, with a significant probability that driving difficulties may
result. Volatility related
problems have been discussed before, and there are a number of often fairly
simple remedies.
Octane
quality
The
addition of 5% ethanol increases petrol octane quality by about one octane
number. For this reason high
octane unleaded petrol (nominally 98 Research Octane Number or RON) is more
likely to contain ethanol than the normal 95 RON standard or ‘Premium’
product. Refiners do not like
giving quality away, so if ethanol is added to the standard product, the
blend may be adjusted so that octane quality remains at 95 RON.
Those owners of high performance cars originally requiring high
octane five star petrol are more likely to buy 98 RON unleaded, so they are
more likely to encounter blends containing ethanol.
However, given the high octane quality of ethanol, and the EU-driven
enthusiasm for bio-fuel inclusion, use of ethanol in the normal 95 RON
unleaded petrol cannot be ruled out. Exposure
of the majority of historic vehicle owners to blends containing ethanol is
increasingly likely as time goes on.
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Effects
on fuel system metals
Briefly,
the presence of ethanol in petrol increases the risk of corrosion of
metallic fuel system materials. This
difficulty is recognised from long experience, and effective corrosion
inhibitors have been developed. Responsible
fuel retailers should employ a suitable additive to protect their
customers’ treasured possessions, but this may not always be the case.
CONCAWE Report 3/08 gives a list of metals not recommended for use
with petrol containing ethanol which reads like a metal who’s who for
vintage and classic vehicles, i.e. zinc,
brass, copper, lead-coated steel. On
this basis, the type of vehicle favoured by those represented by the FBHVC
could have problems in the petrol tank, fuel pipe, carburettor and most
fittings. Modern vehicles have
tended to maximise the use of engineering plastics, so will have less of a
problem. However, to avoid
sounding too gloomy, it should be remembered that corrosion inhibitor
additives are usually very effective in providing protection, and if the
products used by the fuel retailers do not perform, a low cost after-market
product may well become available for owners of vulnerable vehicles to use.
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Effects
on seals, plastics and other materials
Other
no-no materials mentioned by Report 3/08 are shellac, cork, nylon and GRP
materials, plus various elastomer and seal materials.
Recommended materials include Viton, Fluorosilicone, neoprene and
Buna-N
for hoses and gaskets (but neither of these for seals).
Teflon tape is recommended in preference to alcohol based pipe and
thread sealing materials. Tank
lining materials used to prevent small leaks in tanks are also in the
not-recommended category for ethanol fuels.
This is consistent with a report received by the FBHVC this summer
from one owner who had treated his tank with a proprietary sealing product,
after which fuel containing ethanol had been used, resulting in a proverbial
gooey mess. The scale of the
problem in this case led to the need to strip the fuel system.
It is not currently known whether tank sealant manufacturers are able
to supply products compatible with fuels containing ethanol, but their
availability would certainly be an advantage.
If such products are not available, their use is likely to decline
and rather more traditional methods of tank repair, or even re-manufacture,
may become a growth industry.
Effect
on gums, sediments etc.
Over
time all fuel handling systems tend to accumulate deposits of one kind or
another in crevices and corners. Sediments,
gums, rust, lacquer and other materials fall into this category, and
generally the older the fuel system the more of such material there will be.
Unfortunately fuels containing ethanol tend to loosen these deposits
which then move on to plague the driver with mysterious fuel starvation
problems. There have been a
number of references to such problems recently, including in cars used for
racing, which arguably may be more likely to be using fuel containing
ethanol through the high octane route. Irritating
though this problem must be, there is arguably a finite amount of such
material in fuel systems, and thus after a certain time, which will be
shortened by thorough cleaning, further use of ethanol fuels will not
dislodge more sediment to block filters or jets, so hopefully this problem
will fade with time.
Fire
safety
Fuels
containing ethanol at low levels (5-10%) behave very similarly to those not
containing ethanol when burning, so safety considerations and fire-fighting
techniques will be similar. However,
high ethanol content fuels have been shown to be capable of de-stabilising
or collapsing foams used to fight fuel fires.
Also, pure ethanol burns with no visible flame so making fire
fighting more difficult. Alcohol
resistant fire fighting foams should be used with fires in fuel containing
more than 10% ethanol, but given the difficulty of knowing what sort of fuel
blend is in use in certain older racing vehicles, this type of foam would be
a wise choice for all racing applications.
In
conclusion, there are a number of unfortunate or negative aspects to the use
in older vehicles, of fuel containing even 5% ethanol.
These can be summarised as: an
increased tendency to vapour lock, fuel system corrosion and random fuel
starvation events from dislodged deposits.
These potential problems in general would support the view
‘if
in doubt avoid’. Unfortunately
it seems increasingly clear that it will become harder and harder to do
this, so that perhaps inevitably such fuels will become just another part of
the picture of using a historic vehicle in today’s world.
Experience is being gained all the time, so maybe a clearer picture
will emerge with use. Historic
vehicle owners should be aware of potential pitfalls, as they may be able to
take precautions, or may more easily find a suitable remedy for problems which do occur.
From
the Federation of British
Historic Vehicle Clubs newsletters numbers. 3 & 5 - 2008.
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