Performance and Technical
information about engine motor oil for your high performance motorcycle.Choosing the best motor oil is a topic that comes up frequently in
discussions between motor-heads, 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.
| This article was originally written by Ed
Hackett. Full credit goes to Mr. Hackett for this article. The
Motorcycle Performance Guide staff firmly believes in synthetic motor oils. The
information contained in this paper helps explain why differences are seen between
conventional motor oils and the synthetic oils. One of the most noticeable, is the ability
of synthetic oils to maintain higher oil pressure at high air temperatures at an idle in
stop and go traffic. While engines with roller bearing like the Harley engine are more oil
volume dependent than pressure dependent, with very low oil pressure the volume of oil may
also be low. Even very high quality convention oils like the H-D oil will break down
on a 85 degree day idling through traffic. Does the traffic ever slow down at Daytona or
Sturgis? I prefer the safety of synthetic oil.
We apologize for changes made to the original
article. Additional comments from Bike Tech have been added based upon our additional
experience in using various products. |
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 use. 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.
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-viscosity 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 best. 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 (VI) 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 by oil weight
Viscosity /
Brand VI Flash Pour %ash %zinc
20W-50
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
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
170 470 55
Mystic JT8
144 420 20 1.7 .15
5W-50
Castrol Syntec
180 437 45 1.2 .10
15W-40
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
Shell Rotella w/XLA 146 410 25 1.0 .13
Valvoline All Fleet 140 410 1.0 .15
Valvoline Turbo 140 420 10 .99 .13
10W-30
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
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
AMSOIL
168 480 76 .5
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
165 445 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
All of the oils above meet current SG/CD ratings and all vehicle
manufacture's warranty requirements in the proper viscosity. All are "good
enough", but those with the better numbers are icing on the cake. The more expensive
synthetics; AMSOIL, Mobil 1, and Spectro 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.
