You raise some good points. One thing I was perhaps
not clear on is when I use the heavier oil. I only
use it in 'smokers' where it is at an unacceptable
level. The alternative is rebuilding the engine. If
the 50 W shortens the life it is really extending the
life as I would have already spent the money on the
rebuild.
If I had a daily driver that smoked, I'd probably
build it. But a car that gets driven 2-3K a year a 1K
rebuild makes for an expensive cost per mile...
Kerry
--- "D. Dardalis" <dardal@xxxxxxxxxxxxxxx> wrote:
> Kerry and all, please see responses inserted....
>
> At 03:02 PM 9/12/2002 -0700, you wrote:
> >Ok, We need a test case. I hear and understand
> what
> >D2 is saying and actually agree with his words. I
> am
> >struggling with the difference between the theory
> that
> >D2 correctly describes and what I perceive to be
> the
> >real world.
>
> There are cases where the theory and practice
> differ. Often, this is
> because the "theory" does not consider all the
> facts. There could be cases
> that what I said earlier does not always apply.
>
> >In my experience, if you have a car that smokes A
> >LITTLE, especially at startup, then running
> Vavoline
> >40 or even 50W racing oil (non detergent) will
> greatly
> >reduce the smoking AND increase oil pressure.
>
> Let's take one by one. I have heard from more than
> one person that the
> single weight could reduce visible smoke. That does
> not necessarily mean
> that it improves the lubrication. In fact, the wear
> rate could be higher,
> even if smoking seased. The lack of smoke could be
> because the oil does
> not burn but it just comes off the exhaust as
> droplets, or it burns but
> more completely with less visible smoke, or that the
> oil supply to the
> ring-pack is reduced, and I may be missing some for
> sure. We are certainly
> dealing with a very complex problem which is hard to
> explain. The oil
> pressure will increase at the lower speeds when
> cold, because the viscosity
> is much higher. But that does not necessarily mean
> longer bearing
> life. The interesting thing with journal bearings
> is that once oil
> pressure is established (within a wide range of the
> values of pressure)
> most of the time they either work without
> metal-to-metal contact (no wear)
> or they seize (load too high or clearance to high),
> and there is little in
> between. The only time they wear is when starting,
> so its far more
> critical to get the oil there fast, than having a
> bit more oil pressure
> when cold, or at low speed before the bypass on the
> regulator opens.
>
> >The
> >downside is that when it is VERY COLD (40 or less)
> it
> >seems a little harder to crank and oil pressure
> does
> >not pop up quite as fast but still pops right up.
>
> That's exactly my point, this is the only time when
> the journals
> wear. This is a very important drawback if engine
> life is important to you.
>
> >What works for me may be because I have rather
> sedate
> >driving habits but based on what D2 said, my
> solution
> >would actually be better for hard driving except
> >possibly for a few seconds at startup. After all,
> >it's RACING oil.
>
> Well, actually the straight 50 oil will have a far
> worse viscosity index or
> VI (see prior message) than the 20w50 or Mobil 1
> 15w50. So, as far as ring
> and liner wear are concerned, the 15w50 will do
> better. The oil pressure
> will also establish better for the multi weight, so
> I really see no
> advantage on using 50w (which kind-o looks like
> honey by the way, wondering
> if it also tastes like honey!) except for reduction
> of visible smoke. Now,
> why do they call it "racing"? May be it helps
> sales...
>
> >A car which smokes probably has extra clearance in
> the
> >journals and the heavier oil seems to take up some
> of
> >the slack hence higher oil pressure. Yep the heavy
> >oil can get SLOOW when cold but my thinking is that
> it
> >will also stay in place on the journals while the
> >pressure is coming up.
>
> Good point. The main reason you need the oil
> pressure to build up fast is
> the following. When you turn off your car, the
> bearing clearances are full
> of oil that stays there, regardless of the oil.
> When the engine starts
> again, there is a natural "back pumping" of the
> journal that actually
> prevents this oil from coming off the gap, again
> regardless of the oil
> (some machines with plain bearings can operate for
> years without new oil,
> due to this natural back-pumping effect). However,
> what happens in an
> engine is because the bearings rotate fast and are
> heavily loaded, this
> quantity of trapped oil will overheat very rapidly
> due to shear and loose
> its lubricity. Till fresh and cool oil comes from
> the oil pump, this
> quantity of oil will not do very much. This is
> again where a high VI and
> anti-wear additives help.
>
> >Anyway, in 37 years of messing
> >with old cars, this has worked for me and saved me
> >several rebuilds because I won't drive a smoking
> car.
>
> As said before, all oils are now so much better than
> they used to be, that
> there is hardly "the wrong oil". If there is a
> difference between a good
> oil and an excellent oil, you can only see it long
> term. And even then it
> would really be hard to establish a difference
> because there are many other
> factors that determine engine wear (like driving
> habits, climate,
> etc). That's where these controlled tests help, and
> in all these tests,
> the multi weights and synthetics are indeed
> better...
>
> >If
> >someone has a car that smokes a little (enough to
> be
> >noticable and be able to tell if it smokes less
> after
> >the test),
>
> My green sedan smokes when started. I am sure it is
> valve guide seals
> since performance is excellent and oil pressure very
> strong and climbs very
> rapidly. I believe you, the smoke might reduce with
> the 50w. However, I
> think its a small price to pay for long term
> performance and reliability (I
> pulled a plug the other day that has been in there
> since 96, I didn't even
> have to clean it. The car smokes at startup since
> 97). If avoiding smoke
> is very important to you, then....
> D^2
>
>
>
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