On September 23, David Templeton wrote:
>What about synthetic oil in these engines??
This is a question frequently asked by visitors to BMIHT at
Gaydon and is currently the subject of a leaflet we are in
the course of preparing in conjunction with Rover Power
Train and Engine Development to attempt to answer those
queries. At the risk of bandwidth, a summary of the leaflet
content is as follows:
1. What is synthetic?
AFA the UK is concerned, there are two types. One is a FULL
synthetic that is a blend of chemicals and additives for use
in ultra high performance engines. Equally, a mineral based
oil with some elements of synthetic, is known to be called
Synthetic Oil without further elaborations as to its actual
origin or composition. Strictly speaking, this second
version is NOT synthetic because it only contains "elements"
also found in synthetic. Castrol GTX Magnatec is a classic
example of this but Castrol do not pass off their product as
a full synthetic. Magnatec is a lubricant offering the best
of both worlds and is far more suited to the sort of engines
of interest to us.
2. Synthetic must be a better oil because it is designed to
cope with higher stresses and its modern.
2.1 Broadly speaking, a classic car engine will never
experience the operating temperatures, pressures and
stresses found in a modern Formula One Grand Prix engine for
which synthetic is ideally suited. No classic car engine is
likely to be run for prolonged periods at 15000 to 17000 rpm
and it is at these speeds that the properties of synthetic
oil (special polymers and additives) come fully to the fore.
2.2 It should be remembered that full synthetic in its own
way, like mineral oil, has an ideal operating temperature
range and this range is substantially in excess of the
temperatures found in a classic power unit.
2.3 Where true synthetic is used in a classic engine at
lower than normal temperatures for which it is designed to
be used and to be effective, glazing of the bores can
result. This is felt to be because the synthetic does not
reach the temperature where its true worth comes into play.
The paradox is that this glazing tends to generate unwanted
friction and consequently this places greater loads on the
engine and its related parts than it would find with
mineral.
Rover is generally of the view that MODERN mineral oils -
10W/40 or 15W/50 are far better suited to classic engines
than modern full synthetics. It argues, with some
justification that the engines were never designed to run
synthetic anyway. It's also at pains to point out as well
that modern mineral lubes have properties in their overall
blend that enables them to remain highly effective at
substantially higher temperatures and pressures than thirty
or so years ago when they would suffer from additive
breakdown. Now they do not and those conditions are far
higher than most if not all of us are likely to use our
engine. For this reason alone, it does not feel that oil
coolers are an appropriate fitment today and they might even
contribute to running a mineral oil too cool and in such a
situation, the lube will not lubricate as well as it could
if it was allowed to run hotter. It acknowledges that in the
past, coolers may well have proved beneficial but their
fitment now is almost certainly not necessary. The bottom
line of modern mineral versus a full synthetic is that
synthetic will *possibly* not do your engine as much good as
you think it might, it's considerably more expensive than
mineral and the long term benefits are highly questionable.
Summary? Save your wallet contents, use a high grade mineral
oil and change filter and sump contents regularly.
I've got the CC and API specs at work and will try to
remember to bring them home. worth mentioning as well that
these comments are not based on UK operating conditions but
are global. Suppose you could always emulate the Arabs -
they tend to change oil and filters daily, but there is a
price advantage for them.
Jonmac
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