Re: Engine oil

[jlandry@domain.elided (John A. Landry)]

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On Tue, 02 Dec 1997 16:46:06 +0000, zee <zee@domain.elided> wrote:

>Can I get some opinions about engine oil. Friends whose opinion I
>respect have told me straight 40 wt and another recommends synthetic
>20-50 wt. The argument for the synthetic is pretty appealing so I would
>like some other thoughts.

OK... I'm always full of opinions... and I'll be the first to admit I'm
sometimes wrong... but you asked!  I've looked into oil quite a bit over
the years (who hasn't) because I ride and maintain a motorcycle.  You
wouldn't believe the confusion, lies and snake oil floating around
motorcycling circles!  Several years ago, a publication called "Motorcycle
Consumer News" (who accepts no advertising) commissioned a series of tests
at a University to find out which oils worked best in a sample motorcycle.
This touched off a real eye opening shock wave in the motorcycle community.
Basically, good old Mobil 1 automobile oil beat the pants off 99% of the
overpriced dedicated "motorcycle" oils.

My feeling on synthetics is that I really can't say anything bad about
them.  Testing articles I've reviewed have proven they do in fact retain
their viscosity ("thickness") longer than conventional oils.  They are
usually very "slippery" and actually lubricate better.  Because of this,
these oils can "slip" by leaky seals resulting in apparently more drips.
This is why you'll hear people say they're maybe not good for older leaky
engines.  An added benefit of slippery synthetics is slightly better fuel
economy.  Take a look at the energy conservation rating stamp on same
weight synthetics verses conventional oils.  Synthetic brands will normally
be higher.

But with synthetics, you also have to consider whether the added cost is
justified verses the application.  In a motorcycle, typically the
transmission shares the same small amount of oil as the engine does.  The
gears in the transmission have a pronounced shearing effect on the oil's
polymer chains, thus quickly reducing the oil's viscosity... sometimes
substantially reducing the viscosity in just a few hundred miles.
Synthetics resist this effect and can hold their viscosity for several
thousand miles.  So in a motorcycle, the benefits of longer engine life,
better transmission operation and shifting outweigh the higher cost of
synthetics.

Things are totally different in a slow revving IH engine with a huge oil
sump.  My feeling is that you simply don't need synthetic oil as badly in
an IH engine as a motorcycle does.  Sure, using a synthetic can't hurt
anything and may even extend the already extremely long life of an IH
engine, but when you weigh the cost verses benefit, it doesn't seem to be
there to me.  I religiously change my oil and filter at 3000 mile
intervals, and I'd quickly go broke if I used half a case of a synthetic
oil each time.  For my 345, I stick with a high quality conventional motor
oil... I prefer Chevron Delo 400, but I'm not against buying what's on sale
(or has a mfg. rebate) at the time I make my purchase... like Valvoline or
Castrol GTX.  Think how many IH engines are on the road with well in excess
of 200,000 miles and have probably never seen a drop of synthetic motor
oil... mine included.

As to the oil weight to use.  There are some very big single viscosity oil
fans out there, but I tend not to be one of them.  I tried that route for a
while, but when using them, I just can't get past watching my oil peg out
during a cold start and drop to near nothing during a hot idle.  With a
single viscosity you have to monitor the prevailing outdoor temperature
changes and adjust the oil weight accordingly... what a pain!  As I
understand it, in some cases, early multi-viscosity motor oils did have
some problems, making single weights a better choice for engine longevity.
But oil technology has advanced light years since then and this isn't much
of a concern now days.  A properly selected multi-weight is (for most
people) the best choice.

I choose a viscosity based on not only the prevailing ambient outside
temperatures, but also on the condition, age and operation of the engine.
If you have a 200,000+ mile engine, the oil pump and engine clearances are
going to be a bit "loose."  A slightly heavier viscosity is probably in
order so the oil pressure stays higher to protect and better lubricate the
entire engine.  So where a new engine might use 10W-30 in the winter, you
might want to go with 10W-40 instead for an older engine.  In the summer,