From: colfelt@ucsu.Colorado.EDU (Andrew BW Colfelt)
Subject: Re: Synthetics - The Final Word. (+enclosure)
Organization: University of Colorado, Boulder
Date: Sat, 10 Oct 1992 06:01:14 GMT

vesper@kong.gsfc.nasa.gov (Greg Vesper - RMS) writes:

>What is the best oil to run in a high performance engine?

>I drive a 944T and I maintain it meticulously.  I've talked with several  
>mechanics who are down on synthetics.  

>But I've talked with other drivers who swear by synthetics.  I want the best  
>possible engine protection regardless of cost.  

I use synthetic oil in my racebike.  Motorcycle engines rev quite
high and usually share oil with the gearbox, two things you need
good oil for.  

There is no question that synthetic oils flow better than petro
oils when cold.  I refer you to the "starting friction" ads on TV.

Beware, aged vehicle operators: Switching to synthetic oil for
an engine in middle age is probably more trouble than it is worth.
Synthetic oils are thin and slippery, so much so that aging oil 
seals have a hard time containing it.  If your engine is fairly 
new, no problem.  And even if you did replace all the oil
seals for the switch to synthetic, you'd notice a lot more
engine noise, in an older motor that is.

Synthetic oils offer turbo motors a particularly sweet advantage
over petroleum-based oils: not so much Carbon = no coking.


>The same question goes for synthetic transmission fluid.  My transmission is  
>stiff - especially in the winter.  

I tend to relate transmission fluid to automatics, and stiff
transmissions to manuals.  I'm befuddled by your question.

If your looking for synthetic transmission fluid for your
automatic, I would ask you why you bought an automatic Porsche.

If your looking to put synthetic oil in your manual gearbox,
I would say go for it.  You might expect, however, more gear
noise because synthetics are not as thick and cushy as petro oils.
Using any kind of motor oil in the gearbox is preferrable to
heavy gear oils becuase of the detergent and anti-sudsing 
additives.  It would be wise to change this gearbox oil more
often than heavy gear oil because of shearing.  It would
also be wise to use motorcycle oil in this application because
of the anti-shear additives.


>Some definitive feedback would be helpful, preferably from someone who's torn  
>some engines apart and has seen the long term effects of synthetics.

I haven't done this myself, but it was the advice of someone
that had that convinced me.

If I had a new car, I would be using Golden Spectro motorcycle
oil in both my engine and gearbox: 10w40/10w40 in winter,
and 20w50/10w40 in summer.

The following is included for your reading pleasure,
re-quoted without permission or consent of the original
author, whoever that may be:
=======================================================================


Choosing the best motor oil is a topic that appears frequently
in the rec.motorcycles and rec.autos.tech news groups and in the
various mailing lists read by the motoheads on the net.  The
following article is about how to do just that.

Oil companies provide data on their oils most often refered to
as "typical inspection data".  This is an average of the actual
physical and chemical properties of their oils.  This
information is available to the public through their
distributors or by writing or calling the company directly.  I
have compiled a list of the most popular, premium oils so that a ready
comparison can be made.  If your favorite oil is not on the list
get the data from the distributor and use what I have as a data
base. 

The AMSOIL data showed some independent tests against the oil sold by Honda,
Yamaha, Kawasaki Harley, Castrol, and Valvoline.  In all cases the oil
packaged by the motorcycle manufacturer was equaled or beaten by the
other oils. There is no need to pursue them further. They seem
to be packaged for profit rather than performance.

This article is going to look at the six most important
properties of a motor oil readily availiable to the public: viscosity,
viscosity index (VI), flash point, pour point, % sulfated ash,
and % zinc.

Viscosity is the measure of how thick an oil is.  THIS IS 
THE MOST IMPORTANT PROPERTY FOR AN ENGINE.  An oil with too
low a viscosity can shear and loose film strength at high
temperatures.  An oil with too high a viscosity may not pump to
the proper parts at low temperatures and the film may tear at
high rpm. 

Multi viscosity oils are one of the great
improvements in oils, but they should be chosen wisely.  Always
use a multi grade with the narrowest span of viscosity that is
appropriate for the temperatures you are going to encounter.
Multi viscosity oils start with an oil at or near the low end
and use polymers to prevent the oil from thinning as it warms
up.  These polymers shear and burn forming deposits that can
cause ring sticking and other problems. 10W-40 requires a lot of
polymers to achieve that range and has caused problems in some
engines.  Very few manufactures recommend it any more, and some
treaten to void warranties if it is used.  It was not included
in this article for that reason.  20W-50 is the same 30 point
spread, but because it starts with a heavier base it requires
less viscosity index improvers (polymers) to do the job.  AMSOIL
can formulate their 10W-30 and 20W-50 with _no_ viscosity index
improvers but uses some in the 10W-40.  Mobil 1 uses no
viscosity improvers in their 5W-30, and I assume the new 10W-30.

The W means the oil
passed a set of viscosity measurements taken at low temperature
and is suitable for use in the winter.  As a general rule use 5W-30
below 0 degrees F, 10W-30 above 0 degrees F, and a 20W-XX is OK
above 20 degrees F.  Follow your manufacturer's recommendations
as to which weights are appropriate.

Viscosity index is a measure of how well the oil resists
thinning as it warms up.  It tells how well an oil stays to its'
grade as temperatures change.  The higher the number the better.
These numbers can only be compared within a viscosity range.

Flash point is the temperature at which an oil gives off vapors
that can be ignited with a flame held over the oil.  The lower
the flash point the greater tendancy for the oil to suffer
vaporization loss at high temperatures and to burn off on hot
cylinder walls and piston crowns. 
The flash point is also an indicator of the quality
of the base stock used.  The higher the flash point the better.
400 F is the minimum to prevent high consumption.  Flash point is in degrees F.

Pour point is 5 degrees F above the point at which a chilled oil
shows no movement at the surface for 5 seconds when inclined.
This measurement is especially important for oils used in the
winter.  A borderline pumping temperature is given by some
manufacturers. This is the temperature at which the oil will
pump and maintain adequate oil pressure.  This was not given by
a lot of the manufacturers, but seems to be about 20 degrees F above
the pour point. The lower the pour point the better. Pour point
is in degrees F.

% sulfated ash is how much solid material is left when the oil
burns.  A high ash content will tend to form more sludge and
deposits in the engine. Look for oils with a low ash content.

% zinc is the amount of zinc used as an extreme pressure, anti-
wear additive.  The zinc is only used when there is actual
metal to metal contact in the engine.  Hopefully the oil will do
its job and this will never occur, but if it does the zinc
compounds react with the metal to prevent scuffing and wear.  A
level of .11% is enough to protect an automobile engine for the
extended oil drain interval.  We are all changing our oil at
3000 miles or less anyway (aren't we?) so zinc depletion should
not be a concern.  Those of you with high revving, air cooled
motorcycles or turbo charged cars or bikes might want to look
at the oils with the higher zinc content.  More doesn't give you
better protection, it gives you longer protection if the rate of
metal to metal contact is abnormally high.  High zinc content
can lead to deposit formation and plug fouling.

The Data:

Brand                    VI    Flash    Pour    %ash   %zinc

20W-50
AMSOIL                  136     482     -38     ---     ---
Castrol GTX             122     440     -15     .85     .12
Exxon High Performance  119     419     -13     .70     .11
Havoline Formula 3      125     465     -30     1.0     ---
Kendall GT-1            129     390     -25     1.0     .16
Pennzoil GT Perf.       120     460     -10     .9      ---
Quaker State Dlx.       155     430     -25     .9      ---
Shell Truck Guard       130     450     -15     1.0     .15
Spectro Golden 4        174     440     -35     ---     .15
Spectro Golden M.G.     174     440     -35     ---     .13
Unocal                  121     432     -11     .74     .12
Valvoline All Climate   125     430     -10     1.0     .11
Valvoline Turbo         140     440     -10     .99     .13
Valvoline Race          140     425     -10     1.2     .20

20W-40
Castrol Multi-Grade     110     440     -15     .85     .12
Quaker State            121     415     -15     .9      ---

15W-50
Chevron                204      415     -18     .96     .11
Mobil 1                180      430     -55     ---     ---
Mystic JT8             144      420     -20     1.7     .15

15W-40
Castrol                134      415     -15     1.3     .14
Chevron Delo 400       136      421     -27     1.0     ---
Exxon XD3              ---      417     -11     .9      .14
Exxon XD3 Extra        135      399     -11     .95     .13
Kendall GT-1           135      410     -25     1.0     .16
Mystic JT8             142      440     -20     1.7     .15
Shell Rotella w/XLA    146      410     -25     1.0     .13
Valvoline All Fleet    140      ---     -10     1.0     .15
Valvoline Turbo        140      420     -10     .99     .13

10W-30
AMSOIL                 142      480     -70     ---     ---
Castrol GTX            140      415     -33     .85     .12
Chevron Supreme        150      401     -26     .96     .11
Exxon Superflo Hi Perf 135      392     -22     .70     .11
Exxon Superflo Supreme 133      400     -31     .85     .13
Havoline Formula 3     139      430     -30     1.0     ---
Kendall GT-1           139      390     -25     1.0     .16
Mobil 1                  data not available yet, see 5W-30
Pennzoil PLZ Turbo     140      410     -27     1.0     ---
Quaker State           156      410     -30     .9      ---
Shell Fire and Ice     155      410     -35     .9      .12
Shell Super 2000       155      410     -35     1.0     .13
Shell Truck Guard      155      405     -35     1.0     .15
Spectro Golden M.G.    175      405     -40     ---     ---
Unocal Super           153      428     -33     .92     .12
Valvoline All Climate  130      410     -26     1.0     .11
Valvoline Turbo        135      410     -26     .99     .13
Valvoline Race         130      410     -26     1.2     .20

5W-30
Castrol GTX            156      400     -35     .80     .12
Chevron Supreme        202?     354     -46     .96     .11
Exxon Superflow HP     148      392     -22     .70     .11
Havoline Formula 3     158      420     -40     1.0     ---
Mobil 1                150      430     -65     ---     ---
Mystic JT8             161      390     -25     .95     .1
Quaker State           165      405     -35     .9      ---
Shell Fire and Ice     167      405     -35     .9      .12
Unocal                 151      414     -33     .81     .12
Valvoline All Climate  135      405     -40     1.0     .11
Valvoline Turbo        158      405     -40     .99     .13

So what's the best oil?

All of the oils above meet current SG/CD ratings and all
vehicle manufacture's warantee requirements in the proper viscosity. All are
"good enough", but those with the better numbers are icing on
the cake.  The old addage, you get what you pay for, holds true
for motor oil also.  The more expensive synthetics; AMSOIL, Mobil
1, and Spectro offer the only truly significant differences, due
to their superior high temperature oxidation resistance, 
stable viscosity base, and low temperature flow characteristics.
At up to $6.00 a quart and the 3000 mile oil change intervals
that most of our driving dictates, the benefits may not be
realized. The AMSOIL, Castrol, Havoline, Pennzoil, and Quaker
State also advertize that they meet the more stringent European
CCMC requirements.

The best oil is really one that is actually in your engine, 
is clean, and you feel good about using.

Oil additives should not be used.  The oil companies have gone
to great lengths to develop an additive package that meets the
vehicles requirements.  Some of these additives are synergistic,
that is the effect of two additives is greater than the effect
of both separately.  If you add any thing to the oil you may
upset this balance and prevent the oil from performing to
specification.  Slick 50? Well it contains PTFE or more
commonly, Teflon, a name they had to stop using because it was
not an approved use by Dupont.  My chemical dictionary says that
it will not stick to anything, so how they get something that
won't stick to anything to bond to an oily surface is beyond me.
I'm not saying it can't be done but it does cause the skeptic in
this chemist to come out.  Since it is an oil additive I would
stay away from it.  Sure, the FAA has certified it for use in
aircraft, they just certify that it won't do any harm, not that
it does what it claims.  I'll save my 30 bucks for a few extra
oil changes.

The extended oil drain intervals given by the makers of syntetic
oils are for what is called normal service.  Normal service is
defined as the engine at normal operating temperature, at
highway speeds, and in a dust free environment.  Any stop and
go, city driving, trips of less than 10 miles, exterme heat or cold puts the
oil change interval into the severe service category, which is
3000 miles for most vehicles.  AMSOIL, which says their oils can
be used for up to 25000 miles under normal conditions says that
unless you are using oil analysis, you should follow your
vehicle's severe service oil drain interval.

Hope this helps.

-E. Hackett                  
=======================================================================


-- 
Andrew          
Colfelt@ucsu.Colorado.EDU
--