At summer camp, Dr. Donahue wrote,
> Now that synthetic is avaliable in 20W50, I'm tempted to try it in the
old
> MG. But, I've heard horror stories about the stuff going like sh*t
through a
> goose on an old motor. What say the wisdom of the list?
Hey Bob, a quick note on synthetic oils:
+) The leaking problems with synthetics are, for the most part, a
shadow of the first synthetics that came on the market. I'm sure
you know that a certain quantity of oil must seep into some of the
fiber gaskets and cause the gasket material to swell for them to
seal. The first synthetic oils didn't swell the old seals properly
( the kinds in our older MG engines) because synthetics were
intended for new engines. It was an oversight in product marketing.
NEW synthetics and semi-syn oils HAVE the additives to swell the
seals. Leaking is nowhere near as bad a problem as before.
+) Multi-viscosity oils gain their range of viscosities by the addition
of
coiled polymer molecules. The 'coiliness' of these molecules is a
function of temperature. The WIDER the viscosity range of an oil,
the MORE polymers added -- and these polymers have NO
lubricating ability. They DILUTE the oil. In short, oils with wider
viscosity ranges are POORER lubricants. Why include this? Because
the SAME polymers are added to synthetic oil base to make it multi-
viscosity.
Here is my take on this. Thin oils produce less friction and are
better lubricants BUT, they have a lower tear-strength. That is, the
thin film of oil between two pieces of metal is more easily torn
allowing
metal-to-metal contact when the viscosity is low. This is not really
a problem in new, high precision engines but it IS an issue in our old
British iron.
I use Mobil 1 in my 1979 Ferrari 308GTB and it never drips a drop.
It is also a high precision engine with all new seals and gaskets and
holds
6bar (~90psi) oil pressure at operating temperature and engine speed,
and at cold idle. It also flows 9 gallons a minute!
My 1930 Chevrolet (28hp at 2700rpm!) uses straight SAE30 weight
non-detergent oil. It has NO OIL FILTER and flows no oil through
the bearings! Rather, it 'rains' oil down onto the crank and has
'dippers'
on the big ends of the rods, that splash into oil pools in a tray.
Great
technology! I think a magnetic drain plug is a good option on this car!
If I still had an MG or a Triumph, I would run 20W50 Castrol GTX
and change it and the filter every 3000 miles. This would remove
particulate matter from the lubrication system as well as oil-degrading
contaminates such as water and blow-by gasses. It's cheap insurance.
Happy Wednesday!
rick
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