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17. "Which oil is best for my Duck? Can I use car oils?"


This article is from the Ducatis Motorcycles FAQ, by Duke Robillard duke@io.com with numerous contributions by others.

17. "Which oil is best for my Duck? Can I use car oils?"

More Than You Ever Wanted to Know About Motor Oil.

by Ed Hackett (edh@maxey.unr.edu)

(Editor's Note: before you read all this, you might want to consider the
short answer from Julian Bond : "Pretty much any synthetic motorcycle oil
can be used such as Silkolene Pro-4 or the motorcycle version of Mobil 1.
The factory recommend Agip 4T Super racing which is a 5W/40 grade
synthetic." Personally, I think you can use any brand name, so long as you
change it every 6 weeks. :->)

Choosing the best motor oil is a topic that comes up frequently in
discussions between motoheads, whether they are talking about motorcycles
or cars. The following article is intended to help you make a choice based
on more than the advertising hype.

Oil companies provide data on their oils most often referred to as "typical
inspection data". This is an average of the actual physical and a few
common 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. This
article is going to look at six of the most important properties of a motor
oil readily available 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.

The weights given on oils are arbitrary numbers assigned by the S.A.E.
(Society of Automotive Engineers). These numbers correspond to "real"
viscosity, as measured by several accepted techniques. These measurements
are taken at specific temperatures. Oils that fall into a certain range are
designated 5, 10, 20, 30, 40, 50 by the S.A.E. The W means the oil meets
specifications for viscosity at 0 F and is therefore suitable for Winter

The following chart shows the relationship of "real" viscosity to their
S.A.E. assigned numbers. The relationship of gear oils to engine oils is
also shown.

|                                                             |
|      SAE Gear Viscosity Number                              |
|  ________________________________________________________   |
|  |75W |80W  |85W|    90        |        140             |   |
|  |____|_____|___|______________|________________________|   |
|                                                             |
|     SAE Crank Case Viscosity Number                         |
|  ____________________________                               |
|  |10| 20  | 30 | 40  |  50  |                               |
|  |__|_____|____|_____|______|                               |
2  4  6  8  10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42
                 viscosity cSt @ 100 degrees C

Multi viscosity oils work like this: Polymers are added to a light base
(5W, 10W, 20W), which prevent the oil from thinning as much as it warms up.
At cold temperatures the polymers are coiled up and allow the oil to flow
as their low numbers indicate. As the oil warms up the polymers begin to
unwind into long chains that prevent the oil from thinning as much as it
normally would. The result is that at 100 degrees C the oil has thinned
only as much as the higher viscosity number indicates. Another way of
looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that
will not thin more than a 50 weight would when hot.

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. In the winter base your decision on the lowest temperature you
will encounter, in the summer, the highest temperature you expect. The
polymers can shear and burn forming deposits that can cause ring sticking
and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics
excluded) to achieve that range. This has caused problems in diesel
engines, but fewer polymers are better for all engines. The wide viscosity
range oils, in general, are more prone to viscosity and thermal breakdown
due to the high polymer content. It is the oil that lubricates, not the
additives. Oils that can do their job with the fewest additives are the

Very few manufactures recommend 10W-40 any more, and some threaten 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 15W-40 with no viscosity
index improvers but uses some in the 10W-40 and 5W-30. Mobil 1 uses no
viscosity improvers in their 5W-30, and I assume the new 10W-30. Follow
your manufacturer's recommendations as to which weights are appropriate for
your vehicle.

Viscosity Index is an empirical number indicating the rate of change in
viscosity of an oil within a given temperature range. Higher numbers
indicate a low change, lower numbers indicate a relatively large change.
The higher the number the better. This is one major property of an oil that
keeps your bearings happy. These numbers can only be compared within a
viscosity range. It is not an indication of how well the oil resists
thermal breakdown.

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 tendency for the oil to suffer vaporization loss at high
temperatures and to burn off on hot cylinder walls and pistons. The flash
point can be an indicator of the quality of the base stock used. The higher
the flash point the better. 400 F is the minimum to prevent possible 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.
Low ash content also seems to promote long valve life. 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 rarely
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, under normal use. 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:

Listed alphabetically --- indicates the data was not available

Brand                    VI    Flash    Pour    %ash   %zinc
AMSOIL                  136     482     -38     <.5     ---
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      ---
Red Line                150     503     -49     ---     ---
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
Valvoline Synthetic     146     465     -40    <1.5     .12
Castrol Multi-Grade     110     440     -15     .85     .12
Quaker State            121     415     -15     .9      ---
Chevron                204      415     -18     .96     .11
Mobil 1                170      470     -55     ---     ---
Mystic JT8             144      420     -20     1.7     .15
Red Line               152      503     -49     ---     ---
Castrol Syntec         180      437     -45     1.2     .10
Quaker State Synquest  173      457     -76     ---     ---
Pennzoil Performax     176      ---     -69     ---     ---
Havoline               170      450     -40     1.4     ---
AMSOIL                 135      460     -38     <.5     ---
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
Red Line               149      495     -40     ---     ---
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
AMSOIL                 142      480     -70     <.5     ---
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                160      450     -65     ---     ---
Pennzoil PLZ Turbo     140      410     -27     1.0     ---
Quaker State           156      410     -30     .9      ---
Red Line               139      475     -40     ---     ---
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
Valvoline Synthetic    140      450     -40    <1.5     .12
AMSOIL                 168      480     -76     <.5     ---
Castrol GTX            156      400     -35     .80     .12
Chevron Supreme        202?     354     -46     .96     .11
Chevron Supreme Synth. 165      446     -72     1.1     .12
Exxon Superflow HP     148      392     -22     .70     .11
Havoline Formula 3     158      420     -40     1.0     ---
Mobil 1                165      445     -65     ---     ---
Mystic JT8             161      390     -25     .95     .1
Quaker State           165      405     -35     .9      ---
Red Line               151      455     -49     ---     ---
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
Valvoline Synthetic    160      435     -40    <1.5     .12

All of the oils above meet current SG/CD ratings and all vehicle
manufacturer's warranty requirements in the proper viscosity. All are "good
enough", but those with the better numbers are icing on the cake. The
synthetics offer the only truly significant differences, due to their
superior high temperature oxidation resistance, high film strength, very
low tendency to form deposits, stable viscosity base, and low temperature
flow characteristics. Synthetics are superior lubricants compared to
traditional petroleum oils. You will have to decide if their high cost is
justified in your application.

The extended oil drain intervals given by the vehicle manufacturers
(typically 7500 miles) and synthetic oil companies (up to 25,000 miles) 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. Stop and go, city driving, trips of less than 10 miles, or
extreme heat or cold puts the oil change interval into the severe service
category, which is 3000 miles for most vehicles. Synthetics can be run two
to three times the mileage of petroleum oils with no problems. They do not
react to combustion and combustion by-products to the extent that the dead
dinosaur juice does. The longer drain intervals possible help take the bite
out of the higher cost of the synthetics. If your car or bike is still
under warranty you will have to stick to the recommended drain intervals.
These are set for petroleum oils and the manufacturers make no official
allowance for the use of synthetics.

Oil additives should not be used. The oil companies have gone to great
lengths to develop an additive package that meets the vehicle's
requirements. Some of these additives are synergistic, that is the effect
of two additives together is greater than the effect of each acting
separately. If you add anything to the oil you may upset this balance and
prevent the oil from performing to specification.

The numbers above are not, by any means, all there is to determining what
makes a top quality oil. The exact base stock used, the type, quality, and
quantity of additives used are very important. The given data combined with
the manufacturer's claims, your personal experience, and the reputation of
the oil among others who use it should help you make an informed choice.


Continue to:

previous page: 16. "What is the best way to break in my new bike's motor? I've heard thata petroleum-based oil is best for the break-in period, but then I shouldswitch to a synthetic oil. Is this true?"
page up: Ducatis Motorcycles FAQ
next page: 18. "Should I worry about that white scum that seems to appear inside theoil sight glass?"