Edited to HTML (again) by Kyle Hamar, who would like to thank Clint
Chamberlin,cac_at_mtmis1.mis.semi.harris.com for finding and making this
information available to the F-Body Homepage!
- This file consists of Two articles, "Modern Synthetic Lubricants
for Engine Oil Applications" and "All About Lubricants".
- You may wish to jump to the second title, "All About Lubricants"
- Information is also available from AMSOIL
MODERN SYNTHETIC LUBRICANTS FOR ENGINE OIL APPLICATIONS
By: Richard G. Golembiewski, P.E.
RIS Technical Editor
MILWAUKEE, WI - RIS - There's been a great deal of inter- est, of
late, in the performance of synthetic lubricants. Manu- facturers have
enticed the motoring public for a number of years now, with claims for
increased fuel economy, reductions in fric- tion and wear, decreased
oil consumption, better cold cranking performance, and extended drain
intervals. Many motorists howev- er, remain skeptical, as the price of
synthetics is usually much higher than conventional petroleum based
oils. In addition, a great deal if misinformation has circulated
regarding them. Are these claims simply hype, or is there something
here that the average motorist can be interested in? Let's take a
Synthetic lubricants have been around for a long time. Synthesized
compounds are the only thing that will continue to flow at the low
temperatures found in the arctic or in outer space. During the past
twenty years, some of these same benefits have been made available to
the general public. In order to properly examine the role synthetic
lubricants play, and their performance, we need to first look at the
fundamentals of hydro- dynamic lubrication and lubricant properties
Fundamentals of Hydrodynamic Lubrication:
As usually stated in engineering texts, and intuitively grasped by
most laymen, a lubricant is inserted between two moving surfaces to
reduce friction, and the resultant generation of heat and wear.
"Hydrodynamic" lubrication exists when two surfaces are separated by a
relatively thick film of lubricant. A high pres- sure is not required
to separate the surfaces. In a typical engine, plain or grooved
journal bearings are used to hold the crankshaft, piston rods,
camshafts, and other machine components.
Take out a deck of cards. Place the deck on a table, and with your
hand, move the deck horizontally. Notice how the bottom card does not
move, while the top card moves the most. Those in between move too,
with the amount of motion dependant on the height from the table.
What's happening here is that the friction between the table and the
bottom card keeps it from moving. In fluid mechan- ics, we refer to
the layer that doesn't move as the boundary layer. The type of stress
you applied to the cards is called a "shear stress", and is equal to
the horizontal force you applied divided by the flat area of a card.
This shear stress also af- fects the velocity of each card. This
relationship is directly proportional to the shear stress, and the
distance from the table, and inversely proportional to a quantity we
will call the "viscosity". (Actually, it's a bit more complicated than
this, but it's a suitable simplification for our purposes.)
What this simply means is that for a given distance from one surface,
the velocity will be lower if the lubricant has a higher viscosity,
and a constant shear stress is applied. Hence, the viscosity is a
measurement of the internal friction of the fluid, and its resistance
Our example used cards, but fluids are often modeled as infinitely
thin layers. Thus if you drop a steel ball into a glass of molasses (a
high viscosity fluid) it will drop slowly because of the internal
friction of the fluid. Likewise, dropping the same steel ball in a
glass of water, will cause it to drop rapidly because the fluid does
not have a particularly high viscosity.
We will not consider the methods used to measure viscosi- ty, but rest
assured that standard methods have been developed.
One of the problems with this internal friction is that it produces
heat. If we model the fluid molecules as a series of balls connected
by springs, transfer of momentum takes place between the molecules and
the amplitude of vibration becomes greater. This means that it takes
longer for one molecule to randomly strike another, reducing the
internal friction, and hence the viscosity.
This means that the viscosity of a fluid generally de- creases with
temperature, and increases as the temperature drops. If a fluid's
viscosity is a function only of temperature, then it is characterized
as "Newtonian" after Isaac Newton. Unfortunate- ly, the viscosity of
many fluids, engine oils among them, drop with high shear rates. Such
fluids are termed non-Newtonian.
OK, so what's the fluid's internal friction got to do with the
friction between a pair of parts, such as a crankshaft and a bearing?
First, we need to differentiate between thin-film and thick-film
lubrication. Thin films are a problem. as the viscosi- ty decreases,
the lubricant is less able to withstand the loads placed on it. Heat
is generated, reducing the viscosity even further. Surface-to-surface
contact may occur. In thin films, the coefficient of friction between
the two surfaces actually goes up as the viscosity decreases. Such
films are termed "unstable". It is essential then to provide a film
which is sufficiently thick to provide proper lubrication.
If the film is thick enough, however, the coefficient of friction
between the mating surfaces actually goes down as the viscosity of the
lubricant drops. The temperature drops, and the viscosity of the fluid
rises slightly. This acts as a stabilizing effect, and prevents loss
of film thickness.
The designer then, needs to specify the bearing/journal design and
lubricant viscosity (for a given speed) in such a way as to prevent
the formation of a thin film. This means that the viscosity has to be
high enough even at high temperatures. Howev- er, the fluid still
needs to flow at lower temperatures, and there is enough reduction in
friction between mating surfaces at moderately low viscosities to
warrant their selection.
As an aside, the temperature rise can be controlled some- what by
providing a constant flow of oil to and from the bear- ings. While the
temperature in the sump (where we usually measure it) seems high, it's
significantly lower than at the contact surfaces themselves, and
enough heat can be transferred to make a recirculating flow system
desirable. If temperatures become too high, then an additional cooler
can be added.
Lubricating Oil Fundamentals:
So what about the lubricant itself? What kind of specifi- cations does
it have to meet? The American Petroleum Institute (API), the American
Society for Testing Materials (ASTM), and the Society of Automotive
Engineers (SAE) have cooperatively de- veloped specifications for
If you take a look at the top of a motor oil can, you'll find the
following: SAE viscosity specification (such as 5W-30, which means
that it is a multi-vis oil that meets both the 5W and 30
specifications.), an API service classification (such as SF/CD), and
perhaps an "energy conserving" designation.
The SAE viscosity designation, means that the oil meets SAE J300
specifications for cold cranking (if a "W" rated oil) and at 100
degrees Celsius (if without a "W" rating), when proper ASTM testing
procedures are followed.
The API service classification is a bit more complex. You see, an oil
may initially meet the SAE viscosity specification, but when run at
high temperatures for a period of time, its performance may
deteriorate. The API classifications for most engine oils are set for
spark-ignition engines (such as SF, where the "F" is a chronological
designation), and compression-ignition (diesel) engines (such as CD).
Several test sequences are run using a standard engine. For instance,
rust and number of stuck lifters are rated, the viscosity increase
over time (we'll talk about why this happens later) at, say 100
degrees F is measured, and the amount of sludge, varnish, oil screen
clogging, and cam lobe wear is estimated or measured.
These classifications are getting tougher. For instance, the SE rating
for 1972 model cars allowed a maximum of 400% increase in the oil's
viscosity when measured at 100 degrees F after 40 hours. However, the
SF classification for 1980 model cars, allowed a maximum of 375%
increase in the viscosity when measured at 40 degrees C after 64
hours, with subsequent reduc- tions in the other categories. The new
SG rating is even tougher.
An engine may be designated as "energy saving" if they demonstrate
reduced fuel consumption when compared to an SAE 20W- 30 Newtonian
reference oil. With the coming of federally mandated CAFE
requirements, most manufacturers are designating this type of oil for
use in late model engines, and the EPA allows their use.
Just what does an oil consist of, and how can it be com- pounded to
meet these specifications?
Let's look first at conventional oils.
Crude oil as it comes from the ground is made up of a number of
hydrocarbon compounds - primarily paraffins, but it also includes
other compounds. Often, these compounds are sepa- rated by viscosity
through a distillation process. Since differ- ent fractions of the
crude have different boiling points as well as different viscosities,
progressive boiling is used. Those fractions with lower boiling points
are allowed to vaporize, and are collected and then cooled. These
neutral fractions typically have lower viscosities, while the bright
stocks (those with higher boiling points) generally have higher
As such, we can separate oils by viscosity.
But here's a problem. If we compound an oil to have a relatively low
viscosity (or a multi-vis oil with a significant amount of these lower
boiling point/lower viscosity stocks) some of them will vaporize at
high temperatures, resulting in higher oil consumption. What's left
behind has a higher viscosity. Varnish and sludge are also present. If
the decrease in viscosi- ty, amount of sludge, varnish, and cam lobe
wear are too high, it fails the API service test.
That's why a 5W-30 oil that meets the SF rating represents a major
step. Those oils are said to be "energy saving" since their lower
viscosity at lower temperatures (with thick-film lubrication.
Remember, if the viscosity is too low, surface-to- surface contact may
occur resulting in increased friction and wear!) results in lower
part-to-part friction. Yet by passing the SF rating, it shows that
it's still pretty good.
Now, there are many things in the average motor oil than various
refined fractions of crude. Included are various addi- tives, such as
anti-wear agents, extreme pressure (EP) additives, anti-rust agents,
corrosion inhibitors, detergents, dispersants, and friction modifiers.
Most of these are self-explanitory. They are added to enhance the
performance of an oil. The EP additives are put in to help the oil
hold up between surfaces which feature high contact stresses such as
those between the cam lobes and followers. Detergents and dispersants
are put in to help remove dirt and sludge and hold it in suspension,
until it's either removed in the filter, or the oil is changed.
Also included are various oil modifiers such as pour point
depressants, viscosity index (VI) improvers, and seal swell agents.
Pour point depressants are added to inhibit wax crystal growth at low
temperatures. This gives the oil better cold crank- ing performance.
VI improvers are designed to help an oil's viscosity/temperature
performance. Remember that at high tempera- tures, an oil's viscosity
drops. If it drops too low, we lose film thickness, and are in big
trouble! The viscosity index (VI) is a measurement of how an oil's
viscosity changes with tempera- ture, compared to reference oils. The
higher the number, the better. VI improvers are polymer compounds with
interlocking structures (polymers are long chain molecules). Because
these chains are interlocked, they don't move as easily at high
temper- atures and resist viscosity loss. Unfortunately, they don't
necessarily contribute anything to lubricity, and in fact begin to
wear out under shear stresses. As they wear, the oil's VI
deteriorates, and we're left with the old VI improver, which has to be
held in suspension. This is another reason to change your oil
frequently! The VI improver's sensitivity to high shear stress is
significant in that if the shear stress is high enough, the oil may
experience either a temporary or permanent loss of viscosity!
Finally, an oil company may add various compounds which help protect
the base stock, such as anti-foam agents, antioxi- dants, and metal
deactivators. The antioxidants are important as they prevent the oil
from reacting with oxygen at high tempera- tures and forming sludge,
varnish, and lacquer.
So where do synthetics fit in? What are they? The term "synthesize"
means to put together from small bits. Rather than separating crude
into various fractions as is done with conven- tional oils, synthetic
base stocks are made by reacting various organic chemicals together.
For instance, if an acid an an alco- hol are allowed to react, a
compound known as an ester is pro- duced. (As an aside, the aroma
present in flowers is generally produced by an ester. Others include
butter, lard, tallow, lin- seed, cottonseed, and olive oils - although
I wouldn't substitute my favorite engine oil for any of them in my
cooking, or vice- versa!) Other synthetic hydrocarbon compounds are
also suitable for lubricating oils, and manufacturers may blend two or
more compounds together to arrive at suitable properties.
It should be noted that many additives are also made of synthesized
First, though, let's compare a conventional oil to a synthetic. A
synthetic may require considerably less VI improver to have the same
viscosity index. Remember that the VI improver wears out. Synthetic's
are also more thermally stable.
Synthetic base stocks also have lower pour points - often below -50
degrees F, and require little or no pour point depres- sant. In
contrast, bright stocks may stop pouring at 25-30 de- grees F, and
Still, synthetics are a bit more expensive, so compounding one to
compete directly with a conventional oil may not make economic sense.
That's why they are usually made to have superior properties. The
extra performance is often worth the cost penal- ty.
For instance, synthetics can be compounded with very low pour points.
This gives good cold-cranking performance. They may also be compounded
with slightly lower viscosities at lower temperatures (while still
meeting SAE specifications). This helps to reduce friction, and
results in less wear, and better fuel economy.
Now the 5W-30 "energy saving" oils will do the same thing, but as
we've discussed before, to lower the viscosity, these oils may be
compounded with fractions which have a higher volatility. After a
period of time, they begin to boil off or oxidize, leav- ing behind an
oil of higher viscosity. Now, that same oil may meet API SF
specifications, but a synthetic may remain stable for a LONGER period
of time. (Esters exhibit excellent performance in the API test. Other
compounds are very, very good also.) That means that longer drain
intervals are possible.
A word on use. Some synthetic compounds are not compatible with
conventional oils. However, most manufacturers, have recog- nized that
one may add a quart of their product to someone else's, and have
compounded them to be. To do otherwise would be to pass up their
intended market! (As an aside, I try to avoid having to mix
conventional oil, if I can help it. While they are also compounded to
be compatible, the performance may not be the same when mixed
together. It's ok in a pinch, but I don't make a habit of it.) Also,
the lower friction resulting from the use of a synthetic lubricant
makes them unsuitable for break-in.
To sum up, synthetics provide an excellent alternative to conventional
oils - especially if better performance is required. It's your choice!
All About Lubricants
From a talk to Dema Elgin's High Performance Engine Class
DeAnza College, Cupertino, California
By Roy Howell, Chief Chemist, Redline Synthetic Oil Company
Formerly of Lubrisol
Talk given 07 April 1992
Notes taken by Jack L. Poller
Notes not presented in any particular order
Basis of Lubricants
- Separate Surfaces 2) Removal of Heat (up to 1/3 of combustion heat
may be transferred away from engine by oil) 3) Containment of
Contaminants 4) Sealing
Refining of Crude Oil into a Lubricant
- Refining is the process of removing all the bad stuff. The bad
stuff is primarily oxidants. The result of oxidation of the lubricant
is first varnish, then it polymerizes into 'goop'. (SA grade oil will
goop in 5000 miles)
- Add Oxidation Inhibitors.
- Add Detergents. Reacts with oxidized material. Helps keep piston
rings clean (Rings are quite hot). Leaves an ash residue when
combusted. Not used in airplane engine oils.
In an automobile engine, the piston speed (RPM) and therefore piston
tempature changes greatly and quickly. The tempature differences allow
the ash to break up into small deposits, and go into the exhaust or
blow by the rings into the crankcase and lubricants.
In an airplane engine, the pistons are operating continuously at a
single speed, and therefore do not go through heating and cooling
cycles, so the ash deposits would not break up.
Generally, for automobile motor, lubricant is limited to 1% ash
content. 2% ash is asking for trouble (although 2% may be okay for a
diesel engine). Red Line Racing Oils are low detergent. Detergent is
left out because ash can cause detonation.
4) Add Dispersants. Dispersants are ashless detergents, which complex
low temperature combustion byproducts. Dispersants keep partially
oxidized particles in suspension, and help keep the engine clean.
Dispersants can come apart in exterme high temperature.
Average oil filter is a 20 micron filter. Could go down to 1 micron.
Stuff that dispersant holds in suspension is much less than microns
(it is measured at the molecular level, in Angstroms). At proper
temperature, the stuff is not really a problem. Most of the stuff is
Aromatic Hydrocarbons, boil around 180 F, and leave through crankcase
5) Add Anti-Wear additives. These additives chemically react with iron
to prevent welding of moving metal surfaces. Most common additive is
ZDP, or Zinc Dialkyl Dithio Phosphate. What happens is essentially a
chemical polishing of the metal surface.
The surface gets plated with either Iron Phosphate or Iron Sulfate,
both of which are softer than the base Iron. This chemical reaction
occurs in the 300 to 400 F range, and the Zinc is a temperature
controlling carrier (controls the temperature at which the reaction
occurs. When the two metal surfaces come in contact, a small amount of
the surface plating is 'scraped' off of the surface. This is
replenished by more ZDP contact with the metal. This action prevents
the metals welding through heat generated by high friction contact.
The ZDP in the lubricant may last up to 20,000 miles.
6) Add AntiFoam. Anti foam is a surfactant, usually silicone, and
Major Difference is synthetics are not petroleum based.
- Volitility: Synthetics do not evaporate as readilly as Petro.
based. Usually, synthetic lubricants are based on 1 molecule with a
flat distillation curve.
- Better viscosity versus temperature behavior Thin less as they get
hot Thicken less as they cool
- better oxidation stability
- Synthetic Oil has 10% better heat transfer than Petrolium based
Viscosity Index Improvers
Rubber and Plastic Polymers
Start with a base of straight weight Oil. Then add a polymeric
thickener. When hot, the long polymer chain is really moving around,
causing the oil to flow less. When cold, the polymers stick to each
other, essentially comming out of suspension. The polymers are stable
up to about 210 F, where they start to break up. The drawbacks to VI
polymers is that they can cause engine dirt because of their low shear
Viscosity A B C D
High | ' ' ' '
| ' ' ' '
|* ' ' ' '
| \ ' ' ' '
| *- ' ' ' '
| *\ ' ' ' '
| *- ' ' ' '
| *\' ' ' '
| *- ' ' '
| ' *\ ' ' '
| ' *-*\ ' ' '
| ' *\*-*\*-*\*-*\*-*\*-*\*-*\*-*\*-*\
| ' ' ' '
A Shear at Piston Rings
B Shear at Main Bearings
C Shear at Cylinder Wall
D Shear at Connecting Rod Bearings
-+-+ Viscosity of a Straight Weight Oil (Petro. Or Synthetic)
*\*- Viscosity of A MultiGrade Oil (Base with VI polymers)
What this chart shows is that a straight oil has the same viscosity
regardless of shear rate. However, as the shear rate increases, the
shear breaks down the VI polymers, and multigrade oils have less
actual viscosity at the localized high shear rate area.
The weak link is the rod bearings and Cam, in terms of rate of shear.
There is less friction at the piston rings. Anti Wear is much more
important at the cam.
Red Line Water Wetter is a surfactant - reduces the surface tension of
the water. Allows the water to more intimately contact metal. When the
water boils, the surfactant makes smaller bubbles, which makes it
easier for the bubble to be pushed away from the metal surface, and
allow more water to contact the metal.
Water Wetter has a high Ph, but also has silicates, so it can be used
in aluminium radiators. However, if left for a long time, the
silicates are depleted, and damage will occur. The liquid versions of
Water Wetter do not have phosphates.
Discovered by Roy Howell. Some engineers were begging Roy to develop a
corrosion inhibitor to add to straight water for racers, since racers
rarely use AntiFreeze. He did some work, developed Water Wetter simply
as a corrosion inhibitor, and gave it to Huffaker. Huffaker
immediately noticed lower operating temperatures, and Roy started to
You *can* cool an engine to much. The ideal temperature for coolant is
AntiFreeze has 1/4 heat transfer capability of straight water.
Temperature recordings at block water jacket exit, after stabilizing:
Water Anti-Freeze Water Wetter Temperature (F)
50% 50% No 228
50% 50% Yes 220
100% 0% No 220
100% 0% Yes 202
Differences between RedLine and Mobil 1 Redline starts out with a Jet
Turbine Oil Base, which has a higher level of thermal stability, and
they have to add less friction modifiers.
Red Line has 1/2 Cf of Mobil 1.
Viscosity vs. Sheer strength are similar, but Red Line handles high
Can gain 1 - 2% more power by going to a lower viscosity oil.
There is no longer a problem with synthetic lubricants eating away
seals. (Original Mobil-1, no longer available, left out seal-swell).
Red Line blends its lubricants, but does not manufacture the synthetic
Molybdenum in CV Joint Lube
Molybdenum in CV joint lube is important in high-angle CV joints,
especially off-road applications, where wet lub may be thrown from
contact area. The moly provides a dry-film lubrication.
Gear oil viscosity is measured at 150 F vs. 210 F for motor oil.
Therefore, 40 W motor oil is the same as 95 W gear oil.
Gear oil is acidic, motor oil is alkiline. Gear oil needs very high
wear protoection - Extreme Pressure (marked as EP). Therefore, it has
a very high sulfer and phospor content. Sulfur and Phosphate reactions
start at a lower temperature, and Gear Oil has much more additive than
motor oil. This additive is corrosive to copper bearings and bronze
Positraction additives are Friction modifiers - make the base oil much
more slippery. They coat the metal surfaces, and prevent the
stick/slip mode of operation, preventing shudder, and causes smoother
take-up. Friction Modifiers may detract from EP characteristics.
Friction modifiers cause smooth take-up of Limited slip units. For
track racing, FM is probably undesireable, and immediate take-up is
more important. For Street, FM is usually reccomended for more
Gear oils decompose at lower temperature, usually 250 F.
Gear Lubrication Ratings
GL-1 No Additives
GL-4 Suitable for light duty hypoid sets
GL-5 Has lots of sulfer - Heavy duty hypoids
Hypoid type gear sets have a sliding rather than rolling action, and
therefore require much greater wear protection.
GL-5 Should be used in rear differentials.
GL-6 is a heavier weight GL-5. Used for heavy trucks and Tow Vehicles.
Red Line 75 - 90 NS has No Slip, i.e., no Friction Modifiers.
Red Line 75 - 90 has Friction Modifiers.
Gear mesh in Gears litterally chops up and cuts appart the long
polymer chains of Viscosity Index improvers.
Smell of gear oil is from high sulfur content.
Quaiff Differential is a worm gear, and needs a very slippery oil.
Type F - no Friction Modifiers. Ford originally did not want slip in
Dexron - GM - less Cf than Type F
Now Mercon and Dexron II are almost identical.
Red Line does not reccomend DOT-5 Brake Fluid for racing. More
compressible at temperature.
Red Line does not reccomend mixing race oil with regular oil.
Red Line reccomends breaking in an engine on straight viscosity oil.
Can not use silicone brake fluid in ABS systems, as there is no
lubrication for ABS pump.
Can use Race Oil for 3 to 4 Events.
Dont fully pack the hub, as it will just overflow. As it turns, the
bearing cust the grease, and oil leaks out. This oil then provides the
Lubrisol, Dema Elgin, a Ford Engineer all agree that it does not do
anything. According to Roy, to plate teflon on a metal needs an
absolutely clean, high temperature surface, in a vacuum. Therefore, it
is highly unlikely that the teflon in slick 50 actually plates the
metal surface. In addition the Cf (Coefficient of friction) of Teflon
is actually greater than the Cf of an Oil Film on Steel. Also, if the
teflon did fill in 'craters' in the steel, than it would fill in the
honing of the cylinder, and the oil would not seal the piston rings.
Phomblin (Another chemical similar to Teflon, used in polishes) is a
flouridated ether, has low valitility, is very inert, has low surface
tension, and is very expensive. Owned by MontEdison.
Red Line SI-1 - Injector and Valve Cleaner - Removes approximately 1/2
deposits on valve with each bottle.
STP is a VI.
Castrol R is Castor Oil based. Good lubrication, but dirty.
Methyl Lead goes to intake faster than Ethyl Lead. EPA now has
authority to outlaw lead entirely.
Marvel Mystery Oil and Rislone are surfactants and penetrants.
Neo and other Zero Weight oils are actually 0W - 20 multigrade oils,
so as soon as they warm up, they are effectively 20 weight oil.
Engine Temperature Chart (F)
Upper Cylinder Wall 300 - 500
Exhaust Valve 1200 - 1500
Piston Crown 700 - 800
Hydraulic Valve Lifter 250 - 300
Crankcase 200 - 300
Top Ring 300 - 650
Exhaust Gases 500 - 1000
Combustion Chamber 3000 - 5000
Coolant Jacket 165 - 230
Connecting Rod Bearings 200 - 375
Main Bearings 200 - 350
Motor Oil Limits (F)
600 Maximum Useful Range of All Proof Synthetic Motor Oil |
500 ------------------------------------------------ |
--------------------------------- Maximum | |
400 ----------------| | Useful | |
Maximum Useful | Maximum | Range of | |
300 Range of | Useful | Diester | |
Premium | Range of | Synthetic | |
200 Petroleum | Polyolefins | Motor Oils | |
Motor Oils | | | |
100 | | | |
| | | |
Jack L. Poller
Novell, Inc., 2180 Fortune Dr., San Jose, CA 95131
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