Listers
I know this thread comes up for an airing from time to time
but I thought I'd post some 'off the record' comments that
have come into Gaydon over the last few weeks from oil
companies about modern oils - i.e. those which have
synthetic properties in them and others which are full
synthetic.
There's been a bit of a hue and cry in recent months in the
UK as to whether a 'synthetic' oil is suitable or better for
a classic engine. We've received quite a number of enquiries
from owners of different marques along the lines of "what
should I do?" The hue and cry referred to above is that it
appears certain engines with technologies from about early
1950's to very late 1970's have certain components in them
with a rubber type base and these components are in contact
with lubricants. It's evident that in the case of the Rover
P6, there has been an unexplainable failure of parts in the
general area of the timing chain tensioner. Certain oil
companies (I can't obviously identify them) are quietly
admitting the additives they use in their current oils
(0w-30, 10w-40, 15w-40 etc) are not ideally suited to
classic engines of the types broadly in our focus. Their
reasons are broadly these:
1. Engineering tolerances in modern power units are much
tighter than 30 years or so ago and the oil needs to be
thinner (a lower overall viscosity) to maintain satisfactory
lubrication at much higher operating pressures within those
finer tolerances.
2. Modern engines demand an oil which can be more easily
injected under pressure via much smaller drillings and
oilways to important engine parts which parts have a much
reduced dependency on the earlier type of *splash and stick*
lubrication. Because of this, the thicker 20w-50 lubricants
of years back are more suitable to older engines because of
the 'sloppier' tolerances commonly found in those power
units. Quite apart from the fact that the older lube type
has a marginally higher viscosity range, the oil basestock
used in the blending process is thicker as well and this has
an important cushioning effect on reciprocating or sliding
components. Thinner modern oils (that have anything up to
+25% by volume of additives) are acknowledged by the oil
producers as being too thin and are not so well equipped to
provide the cushioning effect. This DOES NOT mean a classic
engine is not being properly oiled because it is - but it is
likely to sound a lot more 'clattery' while it's running.
3. Cleanliness in a modern engine is far more critical to
the engine's effectiveness and reliability than it is to a
classic. It is said that the higher level and different
types of detergent in modern oil is the likely culprit for
premature *rubber* component failure. Equally, the detergent
is having too much of a scouring effect on carbon deposits
which in themselves act as a provisional seal and some of
the rust inhibitors and EP (extreme pressure) agents are
known to be more hostile to certain older types of
non-metallic engine components than their predecessors.
While acknowledging that modern oils are overall better (?)
than their forebears (they have to do a much more demanding
job anyway) the oil companies I've spoken to at some length
feel classic car owners will be doing themselves no favours
by using these lubricants in older engines. They are
recommending owners of cars from the mid 50's to late 70's
that are used for normal roadwork give serious consideration
to the older (recognised brand) oils which are still
available in their almost original blends. It seems these
older types do use some of the modern additives - though not
those listed above which are potentially damaging.
Primarily, these are anti-foaming additives and others aimed
at preserving the structural integrity of the lube itself to
optimise its useful life expectancy. That said, these
features may not have been found in the former blends to
such a level of prominence as they are today, but do improve
the product overall. I submit this info purely on the
grounds that info I've gained from the oil companies is
broadly along the lines of "state-of-the-art-modern is not
necessarily better." I leave it for you to make up your own
minds but for my part I'm glad I've kept to Duckhams Q20/50
or Castol XL Classic 20/50 and this is what Gaydon is
conveying to its visitors in a leaflet. After a sumpful of
modern oil with a high element of synthetic in my Big Six,
things are certainly a lot quieter now with Duckhams and I
think I'll stay in that country rather than ask the old lump
to wrestle with new technology. It was designed to use it
anyway - so I don't think I'll be losing out. No financial
interest etc
Jonmac
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