Olive oil, balsamic vinegar, and castor oil

["Dean W. Cains" <dwc@domain.elided>]

Hello Group:

While the whimsical side of many of us would like to believe that the TA is 


really filled with Olio Extra Virgine di Oliva, and that Aceto Balsamico 
Tradizionale would make a fine and fragrant engine coolant, there are 
constraints that should be considered, and logic must prevail.  However, if 
one really did want to rebuild a TA using a hydraulic fluid of their own 
choice, check out Rich Hirsch's article published in i Saluti several years 
ago:

http://www.geocities.com/motorcity/downs/3837/ta_diy.html

On a more serious note, I do remember very clearly the unique smell of 
Castrol R at vintage races I attended at Lime Rock and Bridgehampton nearly 
30 years ago.  Lots of Lotus 7's and 11's, Osca's, Maserati Birdcage's, 
Porsche 550's and 356's, Jaguar Xk's and even a D-Type once in a 
while.  Most of these guys used Castrol R, which is indeed oil from the 
castor bean plant (Ricinus communis).

As things turned out, now I'm in school for the second time as an organic 
chemistry major, and have access to some interesting texts and reference 
sources that explain why castor oil was so often the racers' oil of choice 
(and remember that the name 'Castrol' is itself a contraction of the words 
'Castor' and 'oil').

For a fluid to behave as a lubricant, it should first be polar enough to 
cling to (or wet) the moving surfaces it is to protect.  Castor oil is 
quite a bit more polar than all petroleum oils, including the synthetics, 
which are themselves derived from petroleum.  The lubricant also must 
withstand the temperatures it will encounter, and must resist boiling or 
evaporating.  And of course, it must be slippery, which generally involves 
its having a large molecular structure.  Castor oil meets those 
requirement, too.  Castor oil is, at the same time, unstable at high 
temperatures, which might appear to be a drawback, but in fact that 
instability works to its advantage.  At high temperatures, above 300 
degrees F., it polymerizes to form even larger molecules, which are even 
more slippery.  These huge, new molecules are rich in esters, which are 
stable to temperatures approaching 700 degrees F., better than any of the 
synthetics.  Many reference books use wet ice sliding on wet ice as a 
standard for comparison of friction coefficients of various materials.  For 
example, wet ice on wet ice has a range of 0.05 to 0.15, with a lower 
number indicating less friction.  Steel on steel, with non-polymerized 
castor oil as a lubricant, has an average friction coefficient of 0.095, 
more slippery than any other oil on the chart.  Castor oil is also 
insoluble with petroleum products, meaning it won't become diluted by fuel 
contamination.  While I have never seen it mentioned in a text, Castor oil, 
used as an engine lubricant, is unfortunately a 'dirty' oil, and it will 
leave behind deposits that are commonly called 'varnishes', which are tough 
to remove because of their resistance to most solvents (I think orange oil 
works well).

I also remember the racers performing a ritual they called "decanting", 
which involved draining the Castrol R from the hot engines, perhaps to 
reduce the formation of those varnishes, replacing the oil for the next 
race after things had cooled.  I think castor oil still has some popularity 
today with model aircraft enthusiasts, but have no real experience with 
that hobby.


Regards,

Dean W. Cains
dwc@domain.elided

'74 Spider Veloce (cable-operated TA, Dex-Cool in the radiator, Mobil 1 in 
the crankcase)
Lutz, FL

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