Re: Synthetic oil alfa-digest V7 #686

[C M Smith <cmsmith@domain.elided>]

Flattened cam lobes due to synthetic oil sounds pretty odd to me. ALFA
specifies 10W 40 synthetic oil for the 164 in the factory shop manual as
well as the owner's manual. No conventional oil is recommended as an
alternate. This is pretty bold in the good old litigious US of A if
synthetics trash camshafts.  After all this is a country which, among other
things, saw GM  successfully sued because their engines were all made in
the same factory but some buyers actually thought "Rocket" V8's were
somehow special. 5W 50 should be fine as the 5W refers to the oil's
performance at "winter" temperatures before the engine warms up, not at
normal operating temperatures where the 50 rating is SAE's assurance that
the oil actually performs at least as well as a straight grade 50 weight at
the same temperature.

Granted, cams have high surface loading with no oil pressure on the actual
rubbing surface and the top of the engine is a place where the oil finds it
hard to get to, but modern oils rely mainly on the ramping effect of
rotating parts, not on pressure, to ensure the lubricant actually keeps the
metal surfaces apart. Those low oil pressures you see at idle on the V6's
are no cause for alarm (specially if you haven't replaced the sender
recently!) because the oil film keeps the parts separated by forming a kind
of floating wedge in the bearings. Oil pressure is needed to provide flows
of sufficient quantities of oil to keep the oil cool (and the lubricated
components cool), the bearings nice and clean, and, most important, to
ensure enough oil gets to those hard to reach places such as cam lobes and
cylinder walls where there is no oil pressure at all when the actual
lubricating is going on.

It is far more important that those cam lobes get oil flowing on them as
soon as possible after start up especially when the engine is cold, as this
is when most engine wear occurs. That is the main advantage of synthetics
for the street driver. If people are experiencing worn cam lobes I would
suspect dirt in the upper oil galleries, premature loading of a cold
engine, dirty oil, or defective hardening on the lobes before I blamed the
oil. Remember that only a thin skin of metal is hardened on the cam lobes,
once that is penetrated rapid wear will follow. The tiniest piece of dirt
can restrict oil flow onto the cam face enough to cause that slight
penetration of the hardened surface and the cam will be gone in very low
mileage. If all the cam lobes were worn I would suspect the oil, maybe, but
one or two?

 Change the oil and filter religiously, do not load or rev a cold engine (
2000 to 4000 rpm is probably fine for a synthetically lubricated short
stroke like the Alfa 6, lower rpm would be better for those longer stroke
4's), use the best oil you wish to afford, and change the oil regularly!  I
follow the manufacturer's recommendations and for my Alfa that's once per
year or every 16,000 km and the oil consumption is the same today as when
the engine was broken in. I use conventional oil in our 86 SAAB 9000 Turbo
because some carbon contamination from the hot turbo bearings is
unavoidable and so extended drain intervals are a no go with Turbo's, plus
SAAB's run loose valve clearances and drink synthetic like water.  The oil
and filter have been changed religiously every 7,500km as recommended by
SAAB and at 212,000 km the engine uses no more oil now than when first
broken in.

Hope this dispels some of the mystique surrounding oil. Oh yes, I'm just a
lawyer so I know how reluctant manufacturers would be to risk being sued
for wrong info in their owner's manuals, but all I know about engineering I
read in some book somewhere! Sorry.

Michael Smith
Calgary, Alberta
Canada
91 164L she's a flyer.

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